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In footnotes or endnotes please cite AIP interviews like this:
Interview of Gerhard Herzberg by Brenda P. Winnewisser on 1989 March 2,
Niels Bohr Library & Archives, American Institute of Physics,
College Park, MD USA,
For multiple citations, "AIP" is the preferred abbreviation for the location.
Early life in Hamburg, Germany; education at Darmstadt; postdoc period in Göttingen, and Bristol, England; setting up his own lab at Darmstadt as Privatdozent; origins of first of his series of books; departure due to Jewish heritage of wife; fresh start in Saskatoon; more books; limited war research; first direct contributions to astrophysics during the war years; three years at the Yerkes Observatory; forty years of work at the National Research Council in Ottawa; Nobel Prize. Experimental techniques include high resolution grating spectroscopy with photographic plates, very long absorption paths, continuous and flash discharge emission and absorption. Contributions in molecular quantum mechanics, quantum chemistry, astronomy and astrophysics, planetary and cometary atmospheres. Leitmotif is hydrogen: H, H2, H3, H3+. Also prominently mentioned are: National Socialism and World War II.
This is Wednesday morning. The second day of our interview (March 2). We discussed the period when you were working in Darmstadt I think rather thoroughly. Now I've read something about your trip to Saskatoon, but I think you should tell us again something about how you suddenly landed in Saskatoon.
Well, I think we did discuss the connection with Dr. Spinks, who had worked in my lab in Darmstadt, and made the connection. The point was of course that the Carnegie Foundation had established a fund for refugees at universities of the British Commonwealth. They offered it to Australia or Canada or wherever. I mentioned this to Dr. Spinks, that this was available, and the university became quite interested in this possibility. They could have my salary paid for two years, I think it was, and then they had to decide whether they wanted to keep me. So that was agreed upon, and I went to Saskatoon officially, as far as the German authorities were concerned, as a guest professor at the University of Saskatchewan. Well, it didn't take long after I arrived, when they told me that they had converted my position to a permanent position, after three months or something like that, and so I didn't have to worry about the future, which was very important to me, naturally.
At that point I'm sure this was very important.
Arriving in Saskatoon, we traveled across the continent by train, of course. Well, actually I did use the occasion to visit a number of universities in the east, both in the eastern States and in Quebec; in Montreal in particular, on the way, while actually my wife was visiting her sister who was living in Chattanooga, Tennessee. We met then in Chicago, and from there on traveled up to Minneapolis, Winnipeg, and from Winnipeg to Saskatoon, but the American Express people in New York who made out the ticket didn't appreciate the fact that there was a nice direct train from Winnipeg to Saskatoon. They weren't aware that there were trains other than Canadian Pacific. This direct train was the Canadian National. Of course this is all changed by now, but for a long long time there were these two railways, and one went to Saskatoon, the other went to Regina, so they took us to Regina and then from Regina overnight to Saskatoon, to make it a little more complicated. Anyway, on the trip across the prairie, of course there was absolutely nothing there. There were a few houses. Somewhere the train would stop and you would wonder why it stopped, and we were quite worried what was going to happen in Saskatoon; did it also look like this? But Saskatoon at that time was a city of 40,000 people, and it was quite normal. We got into a simple hotel which was quite adequate, and stayed there for I don't know how long now, ten days maybe before we had found an apartment. We rented a furnished apartment so that that part was taken care of. In a way it was almost the best time to arrive in Saskatoon, because it was still the fall. We arrived around the first of September or something like that. Classes were starting on the 15th of September. So I was able to get ready and see what my duties were and started lecturing on the 15th of September 1935 in Saskatoon.
Saskatoon is a university town?
Yes, essentially. Well, it wasn't made to be a university town, but they got the university there somehow. It was a big political struggle between Regina and Saskatoon, where the university was going to be, but that was all in the past. It was a nice small university. There were less than 2000 students. There were 100 faculty members, something of that order, and of course you soon learned to know every one of the faculty members, whether it was in science or the humanities. And the reception was very very nice. Everyone was extremely helpful. The head of the physics department had—so I was told later on—had greatly worried what kind of a fellow this person would be who suddenly jumped into his department. And I don't know if they told him....
They took you sight unseen, basically, on Spinks' recommendation.
Yes. It came through the chemistry department, you see, because Spinks was a member of the chemistry department. It was really the head of the chemistry department who was the liaison with the president and who was strongest in supporting my coming there, because he had heard from Spinks of the kind of lab that I had in Darmstadt and this sort of thing, but everything went well. The people accepted me, accepted us.
How large were your classes?
I was teaching a class in elementary mechanics. This was to the students specializing in physics. And the other class was a class at the graduate level, and there were of course not many students in that. I lectured on atomic and molecular structure or something like that in the graduate class. Those were the two classes that I taught. I could check exactly how many students, but something of the order of ten or twenty students. In fact, one of the students in my class in this first year in atomic and molecular spectra or whatever I called it was a young student of German origin. His name was Taube. A year later he got his master's degree and then he was trying to get support to do graduate work at one of the Canadian universities, but he couldn't find any way of support for that, until he finally went down to the States. I think he went to Berkeley, got his PhD there, and eventually ended up with a Nobel Prize. Henry Taube.
Well, that just underlines something I was just going to ask you. I've read your comments about the university you found there, and the encouragement in your research work, and I read Costain's remarks about the remarkable number of people who rose to positions of leadership in Canadian science who all came from Saskatoon.
It's obvious that there were very high standards at this little university.
Yes, the standards were remarkably high. I didn't feel that there was any lowering of my standard necessary in order to accommodate the students in Saskatchewan.
This was a pleasant surprise to you?
Yes, it was a pleasant surprise. Indeed, Dr. Schneider who later became president of NRC, was also one of the students in that class.
So there was already a strong tradition in that the students were getting a good preparation.
Yes. That's right.
So that you could give them research topics?
Yes. Of course, the university at that time did not offer a PhD degree. The highest degree was the master's degree, but they took that rather seriously. The master's degree was really a small PhD you might say, and people did actually do some research work for the master's degree. Oh yes, one other person who had been there before I was there, as a student for his master's degree, was Weldon Brown. He had visited in Germany before the Nazis came, and he was at the time in the field of molecular spectroscopy, so I had quite good contact with him, and I didn't realize until I got to Saskatoon that he was really from Saskatoon. He came from a farm near there. And I to this day have some contact with him. In fact, his name was mentioned in a conversation I had yesterday with this chap who called from Saskatoon. He later on turned actually to organic chemistry, and he was quite prominent in the field. That's another example. And then of course there was also the example, also from Saskatoon, Harry Thode. Harry Thode, a very distinguished scientist. He got his PhD with Urey at Columbia. He then went to McMaster University and eventually became president of McMaster, but he's still working on original work in mass spectrometry. He's a very well known mass spectrometrist, I think. I didn't know him at the time but I learned to know him later, also a very fine person.
So you found it a very active science community.
Yes. There was a background of people from Europe in the farming community, so to speak, and they had the idea that their children should have a good university education and sent them to university, with difficulties, but—
—at that time, I guess, severe financial difficulties, on the prairies.
Yes. Another example, somewhat later was, of course, Alex Douglas, who was brought up on a farm in Saskatchewan and came to the university there and became one of my students, later on one of my closest collaborators. Without him I don't think this lab would have been established the way it was.
He joined you here and then Cec Costain also?
Yes, right, Cec Costain was one of the students in my elementary physics class, before I left just around 1944. Actually he enlisted during the war, and I can't remember now exactly when he was a student. But he did take one of my elementary physics lectures, Physics II, we called it, early in the war. That is when he began to study. And he was brought up very close by Saskatoon, in a place, Sutherland, within a few miles of Saskatoon.
How did your wife find life in Saskatoon?
Well, she also accepted it very readily, or she was accepted very easily and readily. Our son, our first child, was born in Saskatoon, just about a year after we arrived there, so you can sort of calculate when the position was made permanent! The thing I wanted to mention was the fact that at this time in 1936, there was a change: the old president retired, he was the original, the founding president of the university, Dr. Murray, and a new president came in named James Sutherland Thomson. I remember the Thomsons; the president had a very nice house, a little off the campus but on the campus, and they asked us at Christmas time, to spend a day with the little baby born three months earlier. I remember taking everything to the president's house and spending Christmas Day there. It was that kind of community. Everyone was extremely hospitable.
A real community.
So it was a young university, and established high standards from the very beginning, then.
Yes. Dr. Murray was a very good president, no question of that. Indeed, I dedicated my Volume I to him.
I'm sure that was appropriate. Your wife more or less dropped spectroscopy during this time?
Well, during that time, when the children were very small, but she fairly soon took up from where she had left off in Germany.
I remember reading in the introduction to at least one of your volumes that she did a lot of the figures and such.
Yes, she did. That is correct.
—and did a large portion of the work that goes into such a volume.
Yes. But, for example, the final paper on this singlet delta state of oxygen was a joint paper between the two of us, and she did that work while the children were still quite young.
—she kept her eye on what was going on—
Oh yes. And of course, it was a little easier at that time to scan the literature than it is now. Or to keep track of what is happening in the literature.
Yes indeed. What sort of library facilities did you have in Saskatoon, what sort of journals?
That's a good question. Well, it wasn't all that different from Darmstadt, and there were facilities for getting loans from other university libraries. In Saskatoon they had the principal journals. They had the Physical Review. At that time that was the most important thing to have. A lot of the early spectroscopy was published in the Physical Review, even Mulliken's papers, which later went on over to the Journal of Chemical Physics. But the first papers of Mulliken were all in Physical Review, so once you had Physical Review, you had the basis. And they had one or two of the German journals. I think they had even the Zeitschrift für Physik.
So you did not feel cut off from the literature.
No, not at all. All those things worked out extremely well. Of course, the experimental facilities were very very modest. The only spectroscopic instrument they had was a Hilger E 2 spectrograph, a quartz spectrograph. Well, that was something, but it was not what I had set up after a while in Darmstadt. But we got going, and I got another grating from R.W. Wood, and a grating instrument was built up.
You mentioned you brought a few optical components.
Yes, there was this other instrument. There was another prism spectrograph that was made from these optical components that I had brought along. After two or three years, I had enough to keep some students busy with some work, and I also started setting up now a long absorption path. By that time I had got wise to the fact that you could have more reflections. Soon after, this man White published the idea for what we now call the White Cell, in which you have a light beam go through the tube and each time the beam goes through it makes an image of the previous mirror and in that way you conserve the light, while if you just have plain flat mirrors, you soon lose all the light. That really was a very important development for this work in which I was involved about long path spectroscopy, if you call it that, and of course that has gone on until almost today. Yes, it has gone on till today that we use the same system, the White Cell, and many other people do, but I think I was the one who sort of discovered the White Cell, I mean, immediately realized, "that is it", you see. I was aware of the problem and had tried in other ways to get a long path, and here was a way which was obviously far superior, and so I modified geometrical arrangement of the mirrors, and that is the configuration we're still using in the lab in much the same way. Well, of course, the largest long path that I set up was established when I came to Yerkes Observatory, where I had a marvelous optical shop. There was still Mr. Fred Pearson who was the optician of Michelson. He was past retirement age but they employed him just the same, and he made up the mirrors for this big tube, ten inch mirrors.
Ten inch mirrors, and what was the base length?
The base length was 75 feet, that is 22 meters, and it was in the basement of the observatory in one wing there, and it just fitted in. In that path, I obtained up to 200 traversals in the path of 22 meters, so that was almost a path of five kilometers. That was, you might say, the final White Cell.
The ultimate White Cell!
And there you could really see how it worked. I didn't always use 200 traversals, mind you, because the intensity does go down. There are losses. But you could get up to that, and I did use it in the work with hydrogen, which was in a way the principal outcome of the work at Yerkes Observatory.
This was the quadrupole transition.
The quadrupole transition in hydrogen. That really went remarkably well. I mean, it was quite an effort over the three years I was there, but I couldn't have done it without this optical shop.
The hydrogen experiment you also did at rather high pressure.
Yes indeed. The tube was a steel tube, in two or three sections, I forget now how many I had, and it could stand ten atmospheres. So in hydrogen I used up to ten atmospheres, and since I had a path length of five kilometers, that meant the equivalent of 50 kilometers path length, in the laboratory. Well, I did find the quadrupole spectrum of hydrogen.
That was then the most important thing you did with your long cells.
That's right. There were other things done with them. Oxygen, for example.
These were forbidden transitions also in oxygen?
Yes, forbidden transitions in oxygen. As they are now known in the literature, Herzberg I and Herzberg II and Herzberg III system of oxygen in the near ultraviolet, 2500, 2600 angstroms, and the original one that I found in Darmstadt with the first long tube that I had built. That was the first absorption system, but there were two other systems. One was a singlet-triplet transition, and then there was this triplet delta transition, which was the analogue of the one that Finkelnburg had found in oxygen at high pressure. At high pressure, of course, it was a broad system, but in the tube, at the Yerkes Observatory, it consisted of p bands. They were rather weak and difficult to analyze. Actually, Don Ramsay has a much longer tube here, and he worked on those also, and I have now forgotten what the present status is in the field.
I remember hearing about oxygen bands still being extended further in some of the work here.
Yes. He of course used the same White system. But Mr. Pearson, the optician, was certainly exceedingly useful in getting this done in this relatively short time of my stay at Yerkes Observatory. I think he retired two years after my stay there. Just for the critical two years, he was still there and could make these beautiful mirrors.
You were, once more, fortunate.
I was lucky. I had many instances where I was lucky! But we were really in Saskatoon still.
That's right, the long cell took us ahead. You did a lot of writing of books in Saskatoon.
Well, that was a suitable situation. I didn't have at any time more than two master's students, who worked with me, and before the 6 meter spectrograph was built, there was no real facility there to go much further. While I did some experimental work, I felt I had enough time to get some of these books done, which had been started in Darmstadt. I mentioned before that the proofs of the atomic spectra book were done immediately after my arrival in Saskatoon, and so that was published, and then I started with the book on molecular spectra, originally one book and eventually three books.
And each one slightly longer than the previous one.
Yes. A good portion of Volume I, I had already done in Darmstadt. Volume I was published around 1939.
That's when the publication date is. Both versions came out in 1939.
Yes. I came through Princeton on my way to Saskatoon. I visited Princeton University, and I saw Condon. He was at that time the editor of a series of physics monographs of the Prentice-Hall Company, and when he heard that I was just publishing this German book on atomic spectra, he immediately asked me whether I would consider a translation. Then the same applied to the other books, and I felt a little uneasy about doing the translation, because of the time that it would cost, so I got John Spinks involved. He was very quick in translating the atomic spectra and then the first molecular volume.
Apparently. They came very fast.
At least for Volume I. Of course, Volumes II and III were never published in German. They were immediately written in English, while the Diatomic Molecules was originally still written in German. The Translation with John Spinks was done in Saskatoon. Subsequently Volume II was completed. Then Prentice-Hall Company didn't want to live up to their contract about Volume II, and I got the Van Nostrand Company interested. There was an agent of Van Nostrand that came through Saskatoon once in a while, traveling through various university campuses. He was a very nice man and he got quite interested in this problem, and persuaded his company to take on the second volume, with the understanding that the first volume would be somewhat rewritten and they would then republish the first volume also. And then Volume III was to come. Maybe at that time, it wasn't even clear that it would be split again. So Volume II was finished around 1944, toward the end of the war, and it was in print in 1945.
So there was a slight delay there while you were securing Van Nostrand's support?
Yes. But I certainly used my time fairly well in Saskatoon. And if it hadn't been for the, you might say, the lack of interruptions, I wouldn't have finished the books. If I had been, for example, here. Well, I did finish Volume III here in Ottawa, but with very great difficulty, because there are so many other things going on, and I at that time was director of the physics division and so on, so that Volume III took much longer to complete.
It shows up in the date of publication.
Yes, it shows up in the date of publication.
Yes, well, we are all certainly very pleased that you had time in Saskatoon to work on these books.
The university was quite supportive. Indeed, I needed a draftsman, you see, for the illustrations in Volume I, even of the German edition, and I went to the dean of engineering, Dr. C. J. McKenzie (who incidentally later became president of NRC), and asked him for some student who could do this drafting for me, and he recommended to me a student, Lorne Gray, he did an extraordinarily good job of these figures, and there are many of them. This particular student later on became the president of Chalk River, the atomic energy organization in Canada. And he told me much later when I met him, "I'm still proud of having done these figures for you."
He might even have learned something. Did you have a secretary to type up these manuscripts? In those days probably you would have written your manuscripts in longhand.
Well, it was written in longhand originally. Secretarial facilities were put at my disposal at the university, to get this done. I don't remember the details, I'm afraid.
But you don't remember a lack of secretarial support, so apparently you had no problem in getting it.
No, I had no problem there. I just can't remember now, how this was done, but I know there was no problem there.
That's actually the point I wanted to establish, because in writing a book this can be critical.
Oh yes. Of course I had a similar problem, if it was a problem, though it wasn't, when I came to Yerkes Observatory. It was time to have this revised version of Volume I. After Volume II had been published, Van Nostrand wanted Volume I, they didn't want to just reprint what Prentice-Hall had published, so I made a complete revision of Volume I while I was at Yerkes Observatory. There I remember actually the person who typed it. That was the wife of a very brilliant astronomy student by the name of M. Wrubel, who was also a brilliant pianist, unfortunately he died rather early. But his wife was a very intelligent girl and she did a magnificent job of typing this manuscript, the second version of Volume I.
That was also a big job.
That was also a big job. That, of course, went along all the time while I was trying to observe the quadrupole spectrum of hydrogen. Well, we're still in Saskatoon, I guess.
Yes. We haven't really discussed the scientific problems you got involved in there. You started having contacts with the astronomers, and astrophysicists, during this time.
That is quite right. Perhaps one more humorous phase was that I thought, being in Saskatoon and experiencing the cold winters in Saskatoon, I really had a chance to observe the solar spectrum with very little contamination by water vapor lines. And so I set about to set up a heliostat, which they had in the lab.
They had one?
Yes. An old, primitive one but nevertheless it worked, and brought the light into the spectrograph, once we had the six meter instrument set up. We took some spectra, and the spectra were no different from the ordinary ones.
Practically no difference, no. And the reason is simply that there is an inversion layer, and the temperatures in the upper part of the atmosphere have no direct relationship with the temperatures at the surface, and while we had minus 40 degrees C or F (same thing), on the surface, there was just as much H2O in the upper parts of the atmosphere, so that was a complete flop. But actually, when I was in Princeton, on my second visit, I had talked with [Henry N.] Russell, the well known astronomer, and he became quite interested in this problem, and he supported my application to the American Philosophical Society to get funds for me to get a grating. That's how I got the money for the grating. That was a meeting in Princeton in '37, a very nice big meeting on molecular spectroscopy in Princeton. I saw Russell there, and he supported me in this application, and I got $1500, a magnificent amount of money. $500 of which was paid to R. W. Wood for the grating, and the rest was paid to the university for work on the shop work there, that was done to establish the mounting of the grating and all that. So I got my grating more or less on false pretenses. I didn't realize that this wouldn't work. In fact, it was later quite important. The astronomer Kuiper, whom I knew very well, made a survey of the various methods, how to improve spectroscopic observations of stars or whatever, what would be the best location. My observation of the failure of improving the solar spectrum was quite important to him in saying that it's no use going to places that are cold in order to observe. You have to go to places that are high. That's a different matter. He actually was the one who found that Mauna Kau at an altitude of 4000 meters was ideal for astronomical observations. And nowadays there's a whole flock of observatories on that mountain.
Then he made the first suggestion that an observatory be put up there.
Yes, that's right. And he tested it. He went actually up there and tested the atmospheric conditions and that sort of thing. My negative result had some use. That's all I'm saying.
Was this a vacuum spectrograph?
No. With this, once the grating was established and the experiments with the solar spectrum were given up, I did a fair number of laboratory experiments. One I should particularly mention because at that time, it was the early time when I was in Saskatoon, I had a letter from Pol Swings, the Belgian astrophysicist, who said, "We observed here in a comet a group of features around 4050 angstroms and we can't understand what they are. Can you tell us what these spectra are?" he asked me. I looked at them, various times, and I thought (I was then just involved with writing about polyatomic molecules) it was a bright idea to say that this spectrum really looks a little bit like the spectrum of a tri-atomic molecule, and the obvious tri-atomic molecule was CH2. So I had the idea that, this 4050 group in comets spectra was due to CH2, and on the basis of that, I did some experiments with the grating, in which I used a discharge [??] methane the obvious thing: I thought if I had a discharge through methane, at some stage there might be CH2 being formed. I looked at the discharge, and was hoping that I would find something at 4050 angstroms. Well, the first attempt was a complete failure, because the spectrum simply consisted of molecular hydrogen, H2, and of course atomic hydrogen, and CH. But then I noticed, when I turned on this discharge, the very first moment the discharge looked different from what it looked like when it ran continuously. Somehow or other, I had the idea, how would it be if I just turned the discharge on and off and on and off? And lo and behold, with this on-off, I did that just by hand, on and off, on and off....(Later on I used a motor driven switch, but the first one was just done by hand). And lo and behold, in this spectrum there was something at 4050 angstroms. And on closer look, with the grating spectrograph, it was identical with what had been observed in comets. Of that I felt absolutely certain. And of course, having observed it in the discharge in CH4, it was reasonable, I think, to assume this is the looked for spectrum of CH2. And in fact I published a little note about that, to that effect. I hope I expressed it sufficiently carefully. But at any rate—
Did anyone doubt this assignment? Nobody had better experiments but—
Nobody had better experiments, but the disappointment, if you call it that, came only in '49, after I left Saskatoon. There were two laboratory spectroscopists, Monfils and Rosen in the observatory in Liege where Swings was the director, and they had some methane with deuterium in it, CD4. They looked at the same discharge and they got the same spectrum with no shift, proving directly that this spectrum that I thought was CH2 was not CH2, that it was something else. Later on Alec Douglas proved by isotopic experiments with carbon 13 that it was actually C3, this 4050 group in comets. This really started me to get further interested in CH2 and pursue it until the very end, until I finally found it, and that's perhaps for the next section. But the point was also that at the same time, when I thought it was CH2, I thought, now, I really have to get this spectrum in absorption and how can I go about doing that? I had this grandiose idea. There was evidence in the literature, that if you have for example a gas like Ketene KH2CO, by photodissociation it splits into CH2 and CO, and there were some mirror experiments with CH2, as there had been also with CH3, which showed that actually CH2 had been there. At least this was the assumption. So I thought I must try and have a stream of Ketene photodissociated with a mercury lamp, and then see the absorption spectrum of CH2. That is the spectrum at 4050 which I thought was CH2. As a physicist, I had quite a time preparing Ketene. There was no way of buying Ketene at that time anywhere. It took me quite a little while to learn how to make Ketene. Fortunately I had some help from the head of the physics department, Dr. Harrington, who was a very good glass blower, to make, some equipment that I needed for preparing Ketene. And I finally ended up with Ketene. I had the right vapor pressure and everything, so I felt quite proud that I had learned that much chemistry. Then I tried this experiment and of course it was a failure. I didn't see the absorption spectrum of the 4050 group. But of course I still thought it was due to CH2. It was only due to lack of concentration, I mean, there wasn't enough of it to show it in absorption. And that was the situation at the time when I came to Ottawa.
But keeteen does dissociate to give CH2, is that right?
Oh, it does. Yes. As I found out much later.
You were also using Ketene later, to jump ahead, for the CH2?
Yes. That was the other difficult situation. When I came here, I tried to do it in the vacuum ultraviolet, because particularly when it was shown that the 4050 group was not CH2, I still wanted to get CH2. It turns out that if you use Ketene for the vacuum ultraviolet experiment, you don't see anything because Ketene absorbs at the very place where the CH2 absorption is. In desperation, and really in desperation at that time, we used diazo-methane, which is a very nasty substance to work with, and as physicists we were somewhat hesitant to use it. Many people suggested to me, "You forget about that."
Then that finally showed the absorption spectrum of CH2, after 15 or 18 years of effort, from the time when I started in Saskatoon, and had this letter from Pol Swings.
A very long story. The CH2 story, indeed. But this was still gratifying to the astrophysicists, that you had been able to duplicate these lines (i.e. the 4050 group) in the laboratory.
Yes. I was quite pleased by that angle, and that effort, and absolutely certain about that and of course it turned out to be so. There was another piece of work in Saskatoon done with this new grating instrument and that was the work on CH+. I was visiting at the Yerkes Observatory at the time when there was a meeting held at the instigation of Dr. Otto Struve (the director of Yerkes Observatory) on the question of the interstellar absorption lines that had at that time been observed by Adams and Dunham at the Mt. Wilson Observatory; Adams and Dunham had observed a number of sharp absorption lines in the spectra of distant stars which didn't partake in the motion of the star. In other words, they didn't have the same Doppler shift as the other lines of the star. Long before Adams' and Dunham's work the lines of Ca+ (the H and K lines) and the lines of Na had been observed in interstellar absorption, I think it was Eddington who in 1925 first clearly established the fact that sodium atoms and calcium ions occur in interstellar space. Then Adams and Dunham at Mt. Wilson, when they had completed their large spectrograph attached to the 100 inch telescope studied spectra of distant stars and found some additional lines, most of which were due to other atoms and ions for example titanium and iron that were thus established to be present. But then there were several additional lines which they could not identify. They couldn't identify them. They were apparently not ordinary atomic lines. This happened all within one year, I think, around 1941. One of the strongest of these lines was at 4300.3 Å. Swings and Rosenfeld at Liege (Belgium) were the ones who first pointed out that this line fitted exactly with one of the lines of the CH band whose head was at 4315 Å. It was not just one of the lines, it was THE line, the only line that would remain if you had zero temperature. That is it was the R (1) line, that arises from the lowest rotational level (N = 1, J = ½). So there could be very little doubt that Swings' and Rosenfeld's identification was correct, that actually CH was present, the first molecule identified in interstellar space.
The very first assignment of interstellar molecular lines.
That's right. Now, there were some others there; there was in particular a group of three lines, that seemed to have almost the same separation, and the question was, what were these? The meeting that Struve called was mainly in order to discuss what could they be. Present at the meeting, were Mulliken, Swings was there I think, and Beutler, from Mulliken's lab in Chicago, and Edward Teller, who at that time was also counted as a spectroscopist. And a few other people. Indeed, Mulliken suggested that this group of lines may be CH2. He had made some estimate of where CH2 would absorb, and it was just about in this region. But the rest of us were not quite so convinced, and in the discussion between Teller and myself, we came to the conclusion it must be CH+, and that's where the meeting ended. We couldn't do anything better then than suggest possibilities. When I came back from this meeting to Saskatoon, my grating was set up already. I had a good student, Alec Douglas, and we had an apparatus all ready to study various spectra with mixtures of various gases; we put a little bit of benzene vapor in a helium discharge, and lo and behold, we got a spectrum in the region about 4300 down to 3900 or thereabouts. And when we looked more closely, we had a series of bands, the R zero lines of which were exactly, exactly, the interstellar lines that had not been identified! So there could be no doubt that what we had found was a duplication of this interstellar spectrum.
How did you choose benzene then?
Well, that was only in order to have some hydrocarbon.
Yes, but you didn't take methane.
We didn't take methane, no. Pure methane was at that time difficult to get.
Benzene might have been a better source. I don't know.
I think actually acetylene would be the best. Because with CH4 you get a lot of hydrogen lines, of course, H2. With benzene you get much less H2. Or you might get some messy stuff.
These considerations led to the right results in the case of using benzene.
Yes. So the only problem was to prove that this spectrum was really due to the CH+. We had several arguments which convinced us that really we had CH+: the spectrum showed that it was a singlet spectrum; it therefore couldn't be neutral CH. And we eliminated all sorts of other things, and we plotted the vibrational frequency, the internuclear distance, and so forth.
It was rotationally resolved.
It was rotationally resolved, yes. So I don't think there could be any doubt that it was really CH+. That of course was very interesting to the astronomers, at that time. I remember that after we published this, I ran into the chairman of the board of governors of the University of Saskatchewan in Saskatoon, and he said, "I've seen an article in the NEW YORK TIMES where you were mentioned, about CH+." I wasn't reading the NEW YORK TIMES at that time!
So you learned about it from him.
Yes. That's right.
Astronomy has always been a good way apparently of reaching the public.
Yes. That's right. So I established my reputation with the board of governors in this way.
Saskatoon didn't get mentioned in the NEW YORK TIMES very often.
Not very often, no. Anyway, this observation of CH+ on the one hand, and observation of the 4050 group of comets, established my reputation among the astronomers, and caused them, that is Struve, to try and get me to Yerkes Observatory. Indeed this was around 1942, and Struve wrote to me and asked me if I would be interested in a job, and I thought of course that would be quite a step, from Saskatoon to the University of Chicago. But: I couldn't accept it, because we had manpower regulations during the war. The scientific manpower could not leave the country.
Were you involved in any defense-related work?
It was coming up, but that was really not so much the problem. I was at that time still an enemy alien, actually.
You still had your German passport or citizenship?
Yes. Well, I had a makeshift passport, later, somewhat later. But at any rate, I didn't have the Canadian citizenship, I wasn't naturalized.
I remember you told me you didn't get your Canadian citizenship until shortly before you left for Yerkes.
Yes, that's right. Just before.
But still you were someone with technical expertise.
Yes, exactly. No, it was quite clear, I wouldn't get the permission. I didn't object to that. It seemed quite reasonable to me.
Your loyalty had been placed by that time with Canada?
Yes, right. Quite.
Where were you as to developments in nuclear physics?
I wasn't. The only really strange thing that happened one day, I don't know where I was traveling, it doesn't really matter. I was sitting in a plane, and there were two people next to me talking about obviously atomic energy or this kind of thing, and that was the first inkling that I had that there was something going on. And of course when I was visiting Mulliken in Chicago, half the laboratory was closed off to-well, I didn't know either, but one could guess, but I didn't actually engage in guessing very much. The first I really knew was the day it happened, the first bomb.
The public announcement of the first bomb.
Yes. There was in the newspapers this big flash that people had seen in the United States—
—the test in New Mexico.
Yes. But it didn't occur to me that that was it. I remember that I read about it, I was wondering what it was. No, we were really too far removed from the scene of action, that we would have much connection or.
The only Canadian involvement was really through the group from France that came to Canada.
Yes, von Halban and the others.
In Saskatoon you were a long ways away from where they were working.
Later on after this meeting at Yerkes Observatory, I got involved through a chemist, George Wright at University of Toronto, into working on spectra of explosions, ordinary explosions, that is. I actually did handle explosives at the time, and looked at the spectra of the detonations and this sort of thing.
The emission spectra?
Yes. It wasn't really very successful, but I got involved anyway, and indeed for that purpose I got identification papers, other than the German passport. And I travelled to some place in the States, where they had a meeting on this kind of thing. That again was through the efforts of Steacie, who was very good at cutting red tape, you know. I mean, on the basis of red tape I would never have been able to go to that kind of meeting, or even be allowed to have access to some work on explosives and so on, (he was then director of the chemistry division in this building).
What was the beginning of your contact with Steacie?
Actually, that was afterwards, but nevertheless he was the person who was deciding such questions, or could decide such questions, and this committee of George Wright in Toronto was under Steacie. I didn't have any direct contact with Steacie, but Steacie knew of me, and so I got involved in this group. It wasn't really a committee, but I was involved in this work on explosives.
So there were experiments made to find out if the spectra of the emissions of the detonations were useful diagnostically.
If you like, yes.
You mention in your article here that there was a meeting just before the war at the University of Michigan, or that you gave a course of lectures there.
Yes. Well, they had this summer school. They had had it for quite a number of years, and they had some prominent people from various countries coming up there and lecturing. It so happened that Dennison, who was a member of the faculty of University of Michigan, was on leave for that summer. These were also regular lectures during the summer and the faculty wanted me to give these regular lectures on molecular spectra. I was not one of the prominent people to lecture there in the summer school. I was just lecturing a normal course in place of Dennison. But it was at the time of the summer session, which made it very interesting for me, because at that time I got to know Fermi. He was lecturing, and he was an extraordinary lecturer, of course. The clarity of his presentation! I also got to know John Wheeler, who also lectured. Yes, I should have known more about atomic bombs at that time but I didn't. The point was that John Wheeler was lecturing about the paper that he had written with Niels Bohr on fission. And of course, I was aware of the fact that there was a possibility of chain reaction and all that, but the fact that there was actually work done on that, that I didn't know. But at the same time, when I was in Ann Arbor, Szilard was there, and he propagated the idea, I heard him do that at a meeting or a lecture somebody had given. He proposed the idea that there should be secrecy on this. That was in '39. And that people shouldn't publish their results because it might favor or might help the Germans to develop their atomic bomb, this sort of thing.
Did you have the feeling then that he was overplaying this, that it was not necessary to take that so seriously?
Well, I don't know what I thought really at that time, I approved of the idea that it should be secret, but I didn't realize—of course, at that time it hadn't gone very far, 1939. It only was in 1942 that Fermi did the first—
—the first chain reaction.
Yes. But I do remember this mention of the need to keep it secret. That meeting in Ann Arbor, or that summer school was really a very interesting one for me. Of course, the physics department of the University of Michigan was well known for their infra-red work. There were Randall and many others under him. So I tried to use the occasion to look for the spectra of HD+ and H3+ in a discharge. It never worked!
In a DC discharge?
Yes. I tried that here again in Ottawa and it never worked, until Bill Wing and his associates (1976) found HD+ and Takeshi Oka (1980) found H3+ in absorption. I had tried emission.
Do you know now why it was not possible to find it in emission? Was there something to be understood about the mechanism?
Well, you have to have just the right conditions. It took much longer to find H3+ in emission than it did in absorption. But what the real reasons are, I don't really know. I mean, now we know H3+ emission in Jupiter. And there it is.
Yes. Remarkably enough. Well, you stayed at the University of Michigan, this was your only longer visit in an American university during the time you were in Saskatoon?
Yes, that's right.
Did this also maybe help you look favorably at the opportunity that came along with the Yerkes Observatory?
Well, that could be, yes, although I didn't think of that at the time. But I learned to know the people whom I had been corresponding with or had read about in the Physical Review and other journals. There was E. F. Barker and many other people.
So the opportunity to be in contact with these people—
Oh, it was very valuable, yes.
Well, I can see that you were not really isolated in Saskatoon.
In other words, you did come for trips, even under the circumstances in which travel was more difficult at that time than it is today.
Yes. There was also one time, just when the war broke out. I was down in the States and the war broke out, and I wasn't allowed to cross the border back to Saskatoon. I was stopped at the border for three days.
Did they finally just decide to let you go, or did they call Washington?
Well, I tried everything. I called the university and so on. But I was finally let go.
OK, so we've more or less arrived at the end of the war period, at Saskatoon, and then at the end of the war you were free to take a position in the United States.
That's right. Yes. And before that, of course, I got my Canadian citizenship. That was an important step.
You told me you went to check on it and the documents had been lost? Herzberg. Yes. The strange thing was that my father-in-law, who came to Saskatoon late in 1939, just at the beginning of the war, and his wife, got citizenship during the war. Before I had! So something was lost, I'm afraid.
Something had gone wrong, yes. Your wife's parents left Germany just in 1939?
Yes, just after the Kristallnacht, you know. They had thought they could survive in Germany, but after the Kristallnacht, it became clear that they couldn't.
You said your wife had a sister who was in Chattanooga?
Yes. She died rather early. But she had three children, by now grown up.
Did your in-laws stay in Saskatoon, then?
They were in Saskatoon initially, but then my father-in-law got a job in the censorship office, to read German letters, you know, of prisoners of war and all this kind of thing, and he moved to Ottawa, so they were actually in Ottawa before we came here.
John Spinks really started something.
Yes. That's right.
Now you had your citizenship papers, so then you could leave Canada.
This was a position officially as Professor of Astronomy at the University of Chicago?
Yes. There was some complication in that initially the president apparently didn't approve my appointment as full professor but only as associate professor, and I had to make a decision whether I wanted to accept that. Well, I did, and it was later converted to a full professorship very quickly afterwards. The president at the time was Hutchins. I don't know whether you remember the name. He was a very interesting person. I met him only once, really. He made all these changes at the University of Chicago. He was a very powerful personality.
But the Yerkes Observatory was mainly under Struve, the director.
Yes, Struve was the director. Very impressive man, too. Struve came to the United States as a refugee from the Soviet Union, you know. He was in the White Army. He had quite some difficulty establishing himself, but once established his talents were certainly recognized.
His father was an astronomer. Wasn't he?
Yes, very well known. Oh, there was a whole line, his grandfather too. Quite an interesting story.
Well, he certainly played an important role at the Yerkes Observatory.
You had just two graduate students during the time you were there, is that right? It's mentioned here. John Phillips and K. Narahari Rao.
That's right, they were the only ones.
They were not astronomers, they were physicists, I guess?
Yes and no. Yes, they were physicists.
I don't know as much about John Phillips.
I don't know or I don't remember where he got his degree, whether it was in astronomy or physics. But certainly Rao was in physics, and still is.
The interesting thing, by the way, is that Rao's PhD examination was most undistinguished.
And it shows that one cannot predict how a person will turn out later. Well, as I said the other day, he shares that with people like Heisenberg.
Exactly, yes. He has not continued in astronomy, or has not had close ties with astronomy, whereas John Phillips has stayed much closer to astronomy.
Yes, he has stayed much closer, although in a way much closer to spectroscopy, than astronomy in much the same way as I have done. I'm not talking about particular stars or galaxies or this sort of thing. It's mainly the spectroscopic part, the molecular spectroscopic part that I'm interested in.
What was the most important aspect of your stay at Yerkes Observatory then?
Well, we mentioned already earlier that I think the most important aspect was the building up of this long absorption tube, which was used for a number of gases, the most important of which was certainly the hydrogen experiment. That was the real reason for building it. But it then was also used for oxygen and for CO2. The CO2 spectrum was interesting since it had been first observed in the spectrum of Venus. The previous lab experiments with CO2 were all done with short tubes at high pressure, and therefore the lines were extremely broad, and the comparison with the Venus spectra certainly didn't tell us anything about the pressure or density in Venus. But my experiments at Yerkes were done with comparable pressures, that is such pressures that the lines were sharp, and comparable to the sharp lines in the Venus atmosphere. I don't know what it really told us about the conditions in the Venus atmosphere, but at any rate, wherever the lines were absorbed in Venus, the density was low, of the order of one or two atmospheres.
You must have been doing most of this work yourself at Yerkes; you did not have a large number of students.
That's right. Now, let's see. Narahari Rao was involved with one experiment namely the observation and measurement of the third overtone of CO2 with the long absorption tube. I think that was quite a nice paper. But his thesis really was more on CO+ by emission spectroscopy. But my own work was this H2, O2 and CO2 with the long tube. I feel very satisfied about the outcome of that. It was certainly the first observation of the quadrupole transitions in hydrogen. My idea was that this would lend itself to the discovery of hydrogen in Jupiter, and it did. I didn't take the Jupiter spectra, other people did. But the bases were these laboratory spectra of the quadrupole transitions.
That expectation was fulfilled, yes. You checked one other paper on the list of publications, the "Infrared CN Bands" with John Phillips.
That was with John Phillips, yes. Well, Kuiper, whom I mentioned earlier, had built a very fine infrared spectrometer at a time when there were no instruments that you could buy so easily. This was suitable for planetary or stellar observations. The laboratory work we did on CN was done with Kuiper's instrument. The red system of CN had never been extended into the infrared. In earlier work the zero-zero band of this system had been assumed to be at 9140 Å but our infra-red spectra clearly showed this to be the 1—0 band and that the true zero-zero band is at 10879 Å. It was nothing very striking, but at the time it seemed important.
You did not stay very long at the Yerkes Observatory.
Well, it was in a way the lack of communication with spectroscopists. I could go to the campus, but that's a long trip. Indeed, at that time we didn't have a car, so it was a trip by railway or bus, then the University offered me to give me a position on the campus in the physics department, in spectroscopy with Mulliken, but we were a little disappointed about living in the United States at that time. At that time, there was still a residue of rationing, and there was a lot of black market, and of course there was no such black market in Saskatoon! This, among many other things, somehow made us not feel so very happy in Williams Bay where the observatory was or in Chicago, and I mentioned this in a letter to John Spinks at one time. Spinks immediately wrote to Steacie, and said there might be a way. Steacie, perhaps a week after I had written to John Spinks, wrote a letter that he understood that I was not 100 percent happy, would I be open to an offer from NRC? And so it happened.
Did Steacie just know you by reputation still?
At that time, yes, just by reputation. Steacie, before the war, must have been on sabbatical from University of McGill, before he came to NRC, and he worked with Bonhoeffer in Frankfurt, very close to Darmstadt. I don't think I ever met him during that time. Why, I don't know. So it was mainly by reputation. The other point was, you see, the support. One important factor was this, that it was just at that time when I was at Yerkes Observatory, that the Office of Naval Research was founded in the U.S., and they came around to people and encouraged them to apply for grants with the Office of Naval Research, and with the encouragement of Struve and so on, I applied for a grant from the Office of Naval Research. And it was turned down!
Which you were not expecting, apparently.
Which I wasn't really expecting, because I'd heard so many people had got grants. This was at the beginning of the Office of Naval Research and they were quite generous, normally. Well, that didn't help to make it more attractive, because I did need some funds, because the observatory was not all that well funded as such from the university, and the funds were quite limited. On the other hand, NRC offered at that time almost unlimited funds, at least unlimited for the kind of things that I was interested in doing. And complete freedom to do what I wanted to do. At the observatory of course I always felt I had to do something that had something to do with astronomy. And so, there were a number of considerations of this sort that made me wonder, whether I had done the right thing. I never regretted the three years I spent there. For one thing, I was really quite successful with regard to hydrogen and oxygen. For another, as I said before, Chandrasekhar's office was right opposite mine and we had many conversations, and a friendship developed between the two of us that I very much valued, and there were other people like Gerard Kuiper. But except for Chandrasekhar, who had wider interests, the astronomers were really astronomers, and I didn't have the connection with physicists or chemists! All these things together. Here at NRC the offer was that here was a chemistry division, physics division, they were all in the same building at that time and so on.
It was then a rare opportunity to be here at that time.
Yes. And then the question of naturalization. I mean, I would have to wait five years before I could become an American citizen. Here I had citizenship. That I liked. So all these things together. And the children didn't like it perhaps all that well under the conditions in Williams Bay. The schooling was not all that perfect.
Not as good as it had been in Saskatoon?
Not as good as in Saskatoon. Well, it was local, you know, Williams Bay is a very small place.
It's a really small town.
It can hardly be called a town. It's really a village. And the people in the village were not people that you would like to associate with particularly, because they were only interested in tourists. It's a tourist place, really, on the edge of Lake Geneva, a very nice lake. So to stay at Williams Bay was not ideal. To go to the center of Chicago didn't appeal to me, for more than one reason, although I would have enjoyed the connection with the people at the University.
I know James Franck was apparently never happy at Chicago. Did you have contact with him? While he was at Chicago?
I had a fair amount of contact but we never got around to talking about how we liked it in Chicago.
I just remember hearing that from the people at Duke, people who knew him and Hertha Sponer that he just was never fully happy at Chicago.
Is that right? Well, I can well believe that, for very similar reasons to my own, that I wouldn't want to really live in the middle of Chicago. I had an offer, many years after I came here, to go to Toronto University. It was quite a serious offer. But to live in such a big city somehow didn't appeal to me.
Darmstadt was not that big a city at the time you lived there.
I was thinking that Saskatoon is very small, even Ottawa is small compared to Darmstadt today, I think.
No, I think they would be comparable.
Ottawa and Darmstadt are about the same size?
Yes, about comparable, I would think. But anyway, these were all the considerations that entered our minds at the time. I certainly have never regretted going to the U.S. for three years, but I have also never regretted going back to Canada and to then go to Ottawa. It turned out to be a good choice.
So this was 1949. 1948, when you first came to Ottawa.
I came here in August of '48. Of course, there was also a question with equipment here, just as when I came to Saskatoon there was not really much spectroscopic equipment. No grating, nothing like that. But there were at that time certainly funds available to either buy things or build things, and there was a good shop, still is.
The division was just being built up?
No, the division had been in existence all through the war, of course, and much of the war work was initiated in this physics division, which was under a man by the name of Boyle who was just retiring at the time that I came. Again it was really a question of chemistry telling physics whom to appoint, like in Saskatoon.
Since this suggestion had come through Steacie.
Yes, right. Who of course later became the president, but that was somewhat in the future at that time. Anyway, my relations with Boyle were never very close. He I think was a somewhat disappointed man because he thought that he would eventually become the president of NRC and he never did, and he didn't have the capability either.
It was expected apparently that you would develop a new laboratory at NRC.
Yes. This was in spectroscopy. Now, at the time that I accepted, I wasn't aware of the fact that there was a possibility that I would become director of the physics division. That was not really in my mind; I didn't want an administrative job in the first place. But when I did come and then the question of appointing a successor of Boyle came up, Steacie presented it to me in this way: of course I wouldn't know who was coming if I didn't take the job myself. Apart from that, I shouldn't consider the job as keeping me away very much from my own scientific work, and this actually turned out to be true. In the first ten years that I was here, administration was arranged in such a way that I as the director wasn't bothered with all sorts of detail, as I would be. I mean, I spent perhaps one day, no more than one day on the annual budget. I didn't have to prepare long memoranda about why I needed this, why I needed that, and all this kind of thing. And on top of that of course they appointed a co-director who was Leslie Howlett. He's an optical physicist. And he was quite an energetic man, and of course he was a candidate for the directorship also. He took on much of the administrative things that had to be done, and perhaps in some ways a little too much, in that he eventually produced this split in the division into applied and pure physics, which I didn't really like all that much. I thought a good argument could be made for having the two together, and that there would be mutual interrelation. At any rate, the thing that finally settled the matter was, when I found out that plans for an applied physics building on the Montreal Road Campus had been made and practically ready without my knowing about it. At that time, I decided I'd go to Steacie and say, this won't work. And so the division was split into a pure division and an applied division. Howlett was quite a capable administrator, and quite a good optical physicist, I would say, but it just somehow didn't work here. So that's how the pure division arose. Then of course when Howlett retired (I think he was one year older than I was so he retired one year before I would have had to retire if nothing had been done about it), then the question of the successor of Howlett came up. The committee decided on Alec Douglas, and he wanted the division to be recombined. He felt that it was not wise to have them so separate. And I think rightly so. And on that account, I retired as director of the pure physics division at the same time, that was in 1968.
Then the two divisions were reunited as one division.
That's right. But the trouble was, of course, Alec Douglas was not all that much interested in administration, but he still took it fairly seriously. There were then developments, toward more bureaucracy which upset Douglas so much that he resigned as director of the physics division, and went back to be in charge of the spectroscopy laboratory. And I think he was quite happy about the eventual solution.
Yes. So those first ten years were in many ways a golden age.
Yes, in many ways, because Steacie of course had taken over from McKenzie around 1952, and his presidency was certainly the high point of NRC as an organization for pure and applied research, but with some emphasis on pure research, I would say. And of course that one cannot say now.
Not in the way it's being planned.
No. But I don't know that anybody can be blamed for it, but of course the politicians don't understand pure research or the importance of pure research, that even if you're only interested in applied research, you've got to have pure research.
Yes. At the beginning you started building spectrometers, and then there was the question of who should come to work with you.
Yes. Well, I was of course extremely lucky when Alec Douglas agreed to join me in building up this spectroscopy lab. Without him we wouldn't have come as far as we did by a long long shot.
Were you given a fixed number of positions you could fill, or was this allowed to sort of develop?
It was more or less allowed to develop. At that time, things were not so tight. There were a number of positions for the whole of NRC and they were never all filled at that time, because of course one wanted to get good people. I had to do something about appointments to the division, the whole division in various fields. There was for example the appointment of somebody for solid state and low temperature research. I got a recommendation for a man from Oxford by the name of D.K.C. McDonald who was apparently a very good man, and he came and it turned out to be a very good appointment, although unfortunately he became ill after perhaps ten years of his stay here. He had this awful disease that afflicts Stephen Hawking. I think for Stephen Hawking the disease has been arrested in some way. It was not possible for D.K.C. McDonald, although he worked up to the very last. He came into the lab on a stretcher, and dictated letters and this sort of thing. But it was a very sad affair. Anyway, that was one of the people that came.
As director of the division of physics, you certainly influenced the appointments not only in spectroscopy but in the rest of physics.
Yes. But on the applied side it was more Howlett who looked after it, even when the two were still together. He for example got a very good man for photogrametry: T. J. Blachut(?) who established an international reputation. He got a number of very good people, and on the whole I think the appointments were made fairly well. Just the year before I came, Steacie had introduced the system of postdoctoral fellowships, which was mainly a way of taking up some of the positions that were open. As I said, the number of positions at NRC were larger than the number of people actually there, and in order to not fix everything and to have some change, some turnover like at a university, he had this idea of postdoctoral fellowships which were operating positions that were there but were not filled. They were temporarily filled by these postdoctoral fellows, and I think that was a very good arrangement. We profited from that in spectroscopy and we had of course a fairly large number of fellows.
Yes indeed. So you started using these very early then.
Yes. It's quite a large number of years ago, that I don't remember who were really the first ones.
I'm sure there's a list somewhere of these things.
Yes, there's a list. In fact, I think Rao finished his thesis here in Ottawa, if I remember correctly. Anyway he came here and he was here for some time. We then had also another appointment that was made soon after I came. This was Hin Lew who had worked on atomic beams and set up an atomic beam apparatus successfully, and this was a different angle in spectroscopy that I was quite anxious to establish, and so that was another appointment. Then Don Ramsay was in chemistry and he was with Norman Jones, you know.
He started with Norman Jones?
He started with Norman Jones. But Steacie then suggested that if I liked, we might be able to take him over, which we did, and so he was another appointment on the staff rather than a postdoctoral fellowship. Still another was Cec Costain who established the microwave lab. I think those were probably the main permanent staff members at the time. And then we had quite a number of postdoctoral fellows. One of the early ones, come to think of it, was Peter Brix. He had of course worked in nuclear spectroscopy, that is, hyperfine structure work with Kopfermann.
I knew he was a nuclear physicist, that's why I was surprised when I saw his name.
Yes. He spent a year here and did a very nice piece of work on oxygen, which was done jointly between the two of us. I'm still corresponding with him off and on. He has of course done extremely well in Heidelberg. I was very impressed. He sent me the speech he gave in Berlin on the occasion of the 50th anniversary of the discovery of fission; a very fine accomplishment (I mean the speech). But Peter Brix stayed on his fellowship here only for a year. Then he went back, I think, to Darmstadt at that time.
Well, you certainly had people coming from many countries.
Many countries, that's right. From Japan, of course; from India... One of the early ones from India was a man by the name of Sharma, who was then at one of the Indian universities. He retired some time ago. I just had a letter from him the other day. And, of course, Narasimham was one of the best of our Indian postdoctoral fellows. He worked in the States with Rud Nielsen. Anyway, he came very highly recommended and he was very good indeed. He was then later in charge of the spectroscopy lab of the Bhabha Atomic Research Centre in Trombay.
There are of course strong spectroscopy groups in many universities in India. In other words, there are many people who apply for postdocs with some sort of spectroscopy experience.
Yes. Well, certainly the group in Trombay is a very good group. Narasimham had something to do with it. In fact, it was Narasimham who invited me to give a lecture, when Asundi died. He arranged for having a regular memorial lecture. I gave the first Asundi memorial lecture in India. I didn't really want to go back to India because it's hard to travel there. But I felt that Asundi was an old friend and such a distinguished spectroscopist that I couldn't very well refuse to do that. It was Narasimham who made the arrangements in Bombay at the Bhabha Research Centre, where this lecture was given. I must have had a thousand people listening to that lecture, of which perhaps 10 percent understood what I was saying!
That was after you won the Nobel Prize?
Oh, long after, in November 1984. We just went out to India and back. But like so often happens, just the last evening before we left or returned I had a terrible attack of stomach flu or whatever you want to call it, because of eating some of the wrong things. Fortunately I had the right medicine with me and I could just get cured before the plane left. The plane left in the middle of the night.
I'm glad you were well prepared. Now, during the time that you were director of physics here at the NRC, you also had other roles. I'm thinking about committees that would decide on support for universities.
Yes. Of course, the National Research Council had the function of an NSF at the time, and Steacie got me to look over the grant applications in physics, and I was then present in the sessions in which these grant applications were decided in the actual council meetings. So that took a fair amount of time, yes.
Was it administered so you would determine who were some of the referees, or how was this done?
Well, first it was just done on my say so, in physics. But then the numbers increased and eventually it was necessary to have referees. It wasn't done all that consistently, if you like. A lot of freedom was given there and that was a good thing, I think. While first I was the only one, then a committee was formed for physics, and I was simply preparing things for this committee and we had some very good people on this committee. That was before we had any referees. In fact, I think while I was in charge of this operation, we never had any referees. We only had this committee.
OK, Canadian physics was small enough so that you knew what was going on.
And between you, you could make what you considered reasonable decisions?
Yes, that's right. And there was less preparatory work on that account than there is now. Of course, now it's outside NRC anyway.
Was the NRC then in a position to, say, deliberately help build up a research program at certain universities that you felt needed special support?
Yes, there was that sort of thing. Also then there were major grants that were separated off from the individual grants. It became more and more elaborate and complicated, and while I didn't approve at the time of the separating of this activity from NRC, in the long run I think it turned out to be probably a good idea, because it would have involved too much work for the NRC people and would have kept me more from my own research than I would have liked.
Would you like to comment on these first ten years, comment on what subjects of your research come to your mind then as the ones that you consider the most important during this time?
Well, perhaps we should first discuss the further development of the work on CH2. At the time that was certainly one of my principal interests and I was very anxious to get ahead with that. It went back to the times in Saskatoon when I had done these experiments in preparing ketene and trying to produce CH2 by the photo-dissociation of ketene and then look at the absorption spectrum; that seemed to be the best method of getting a spectrum of CH2. Of course, at the beginning of my stay here, I didn't have any vacuum spectrograph or for that matter any larger grating spectrograph. They had to be built, and fortunately with Alec Douglas' help that went on fairly promptly. I was also fairly lucky in 1949, that I got Mr. Shoosmith as my chief technician, who was working only for me, and that was the advantage of being in charge as the director, that I could assign one technician to myself! As I mentioned yesterday, he was recommended to Steacie by Professor Almand who was also Spinks's teacher, Almand at King's College. Shoosmith wanted to come to Canada because both he and his wife had some relatives here in the Ottawa area. Well, according to the report of Almand, he looked like a very good man, and so we brought him over and it turned out it was a very good appointment. He was what you might call a self-starter. You could leave him with some problem and he would be sure that something would happen. He was also a skilled glass blower. He came in '49, and he retired in '69. Yes, he was with me twenty years. And that was certainly a very good period from the point of view of my research. He was the one, for example, who took over the building of the 3 meter vacuum spectrograph, while Alex Douglas Started to build the 6 meter spectrograph in air, and both of these instruments I think were built during the first two years that I was here, and Alec Douglas was here. Of course, the rooms had first to be built, because there was no floor, where you now walk downstairs, below this office, because it was a large high room for some high voltage X-ray equipment that we didn't need at the time. So it wasn't all that trivial, but with the help of people like John Shoosmith and Alec Douglas, it was possible to get this all done in fairly short order. I was very anxious to work on this problem of CH2. Now, the question was, how to start and I think the start was, if I remember now correctly, that Don Ramsay and I decided we'd try a simple case, namely NH2. There was a spectrum already known that was assigned provisionally to NH2, the so-called alpha bands of ammonia which occur in electric discharges and in flames, ammonia flames and this sort of source. We wanted to try a photolysis experiment on that. That is, we irradiated ammonia with a flash of light and then looked at the absorption spectrum at various times after the flash. And in that way, we observed for the first time in absorption the alpha bands of ammonia, making it very likely that it was NH2. But then Ramsay and Dressler did very magnificent work on the analysis of the spectrum, because this was an asymmetric top and was not all that easily analyzed. But they did, and I think that was completed in 1956. But in the meantime, the vacuum spectrograph was completed, and so I decided I'd have to do some work in the vacuum ultraviolet. I took on that job myself with Mr. Shoosmith as my helper. As I said earlier, we took for example ketene and looked at its absorption spectrum and then flashed it with a flash discharge, looked at the absorption spectrum immediately after the flash discharge, and of course we didn't see anything of interest. Well, in the meantime we had other plans, like CH3. It was fairly well established that if you had, for example, dimethyl mercury or some compound like that and you irradiated it with light, you would get CH3, according to experiments of Paneth in Germany a long time before the war, by some mirror removal experiments, but nobody had seen the spectrum of CH3 at that time. So before we looked at ketene, we looked at dimethyl mercury or some similar compound, even acetone works quite well, and we found indeed in the flash photolysis of acetone or dimethyl mercury not only a band in the non-vacuum region, 2060 angstroms which we thought was due to CH3, but then we found a Rydberg series, below 1500 angstroms, in the vacuum region. Acetone was in that case not very good because it absorbed in the vacuum ultraviolet, but dimethyl mercury didn't absorb very much, and indeed, it allowed us to see the complete Rydberg spectrum of CH3. Then we did the same thing with the deuteriated compounds; we had the advantage of having the help of a very good isotope chemist, Dr. L. C. Leitch. He supplied us with deuterated dimethyl mercury and deuterated ketene and other compounds, so we could prove that the spectrum that we had was really CH3 of the radicals that I felt responsible for, with the help of Mr. Shoosmith. In fact, his name appears on the first publication of that work because he was really very very good in doing this work while I was doing some traveling!
So the CH3 yielded to your efforts before the—
—yes, before the CH2. Then we came back to CH2. We tried some other things. I don't remember all the other things we tried, but as I said before, in desperation we thought we had to try with diazomethane in spite of its nasty properties. Well, Mr. Shoosmith learned how to work with diazomethane and he never had any explosion with it.
Never any explosion? That's very good.
Well, there was one very minor one, but...
We used it in our laboratory and we had one or two small explosions.
Well, in the vacuum ultraviolet, absorptions if there are any, are usually strong and you need very little of the gas, and Shoosmith was careful. We didn't prepare a big amount of diazomethane at a given time, only a very small amount on the order of milligrams. And even if there had been an explosion, it wouldn't have been a very bad one. As long as we stuck to that rule, I think it was all right. Anyway, with the diazomethane we finally observed something that looked like the right thing. We found something, and the question was now, is it really CH2 or is it something else? It could well have been. And so, of course we had again to go to our friend Dr. Leitch and try and get some deuterated diazomethane. And then we found that this spectrum that we had first observed in ordinary diazomethane first of all was shifted, but more than that, it had a fine structure, while the non-deuterated diazomethane didn't have a very clear fine structure, at least in the first experiments. Later on we found that there are diffuse lines that could also be analyzed, but the band of CD2 was really the decisive spectrum. I still remember the day when Mr. Shoosmith got this spectrum. He came up to my office, and I was involved in something or other, and I said, "Well, I have an engagement." There was a seminar coming up and so on. "Well," he said, "you must come down." And I did! I remember the people from the seminar all came with me, and they all looked over my shoulder, and here it was, as clear as anything, intensity alternation and all, of a band that was clearly a molecule with two identical nuclei and since it was shifted, there could be no doubt that this was CD2. And of course that was borne out by further experiments. The final paper on this subject was my Bakerian Lecture at the Royal Society in London which was in 1960. The actual first observation was in 1959. And of course we again (thanks to Mr. Shoosmith) we also looked in the visible region and we found there were some absorption lines in the visible region, and we established that there were two kinds of CH2, which we decided were triplet CH2 and singlet CH2, and we even came to the conclusion on the basis of our experiments that the ground state of CH2 the triplet state, while the singlet is an excited state. And indeed the spectrum that Mulliken had predicted and talked about at the meeting at Yerkes Observatory, about the interstellar lines (he had said that there must be a spectrum of CH2 around 4045 Å), that was a singlet spectrum that he had predicted, and that was the spectrum that we then discovered a little further along, with wavelengths around 6000 and up, and so that fitted together. Of course Mulliken at the time didn't know whether the triplet or the singlet state would be the ground state.
It's not a large energy difference.
It's not a large energy difference, which has now finally been pinned down very accurately by the work of Phil Bunker and Trevor Sears and Bob McKellar in this lab. But the evidence that the triplet state was really the ground state was that when we looked at the timing of the absorption spectrum relative to the initial photolysis flash, we found that the ultraviolet absorption, which is the triplet absorption, persists longer than the absorption in the visible region (or the red part of the spectrum), indicating that the molecules eventually come down to this ground state, and it's a longer lasting thing. That was indeed confirmed later by many other experiments. That was in a way the end of the story of my own efforts in finding the spectrum of CH2 and CH3.
Then there was a problem with the structure of this triplet ground state.
Yes, that's right. That was just a little bit later. From the appearance of the band, I felt fairly sure that the triplet CH2 must be a linear molecule. The band looked so simple just like that of a linear molecule, the right intensity alternation and all that, triplet sigma G minus, like the oxygen ground state. But there were some calculations that seemed to indicate that the triplet ground state must be bent. As a consequence John Johns and I wondered whether there could be any mistake in the original conclusion that it was linear. The only way we could see was that what we were observing was a bent system in which all the higher K levels were predissociated, and therefore we didn't see them. We had also a spectrum of CHD, which also was a nice sharp spectrum, and we could interpret the spectrum then on the basis of a bent structure. Indeed if we took the results for CHD and CH CD2 together we could get a rough value for the angle, if we assumed it was bent, of the order of 130 degrees, which matched the prediction from theory fairly well, and we published a paper to that account. That was in 1971, 12 years after the first observation of the CH2 spectrum.
Yes, it was a long period in between. This interpretation remained consistent with the later developments.
Yes. That's right. Very much so. Surprisingly so, I would almost say, because ours was based on rather uncertain evidence, I should say; we really couldn't pin it down with certainty.
It was a qualitative interpretation.
Yes. That I think was my last publication on CH2. Except for review articles.
Well, the most important aspects of the radical had been established then.
Yes. So after that what other work should be mentioned? What would you like to question about?
Well, I must admit I hadn't made myself a good outline for this part of the discussion yet. We've progressed faster than I had expected. You've done some work on the Lamb Shift. You mentioned just briefly earlier, you measured the shift for the ground state of hydrogen, but the work on helium and lithium was actually more interesting.
Yes, that is right. I don't know exactly why I became interested, but it struck me, that the original work on the Lamb shift was always about the 2S state of hydrogen, and I wondered, surely the 1S state of hydrogen must have a larger Lamb Shift, and indeed according to the theory, it should be larger by a factor of 8, 23 than in the 2S state. And I thought one should be able to discover that, if one could only measure the position of the Lyman alpha lines of hydrogen with sufficient accuracy. So I did some experiments: the problem was to make an absolute measurement of the wavelength of the Lyman alpha line; the interval you want to measure is a large interval because there's no other neighboring state. I mean, the normal so-called Lamb Shift that Lamb measured is between two energy levels very close together, measured in the microwave region, but here, the nearest level to the 1S level is the 2S or 2P level, and this energy difference is Lyman alpha. If you wanted to measure the Lamb Shift, it's a tiny change of that big energy difference and this change is of the order of 0.27 cm-1. So it requires a rather accurate measurement of the Lyman alpha line, which I tried to accomplish. The question was, what kind of standards can we have? I had the idea, which I think was quite good, to use the spectrum of mercury, because first of all the mercury line 2537 is very accurately known, and the higher lines can also be measured fairly accurately, and therefore transitions from the ground state of mercury to one of the Rydberg levels of mercury that lies in the region of the Lyman alpha line would be suitable standards. And this indeed happened to be the case, and in that way, I think I got a reasonable value. What I measured was actually for deuterium because the Lyman alpha line of hydrogen is very broad, in fact it's a doublet of course but the doublet feature is hardly resolved, but in deuterium, the line width is less and therefore it's easier to determine the positions of lines. This is what I did, and I got 0.26 instead of 0.28 or something like that. In other words, within about 10 percent I got a value as predicted. I had hoped of course for a value that didn't agree with theory, but this didn't turn out to be the case. Later on, much much later, Schalow and Hänsch did a far more accurate determination of this shift by using the two-photon transition from 2S to 1S, and got a far better value for the Lamb shift. I don't remember the exact numbers, but I felt I had not done too badly by having observed this for the first time in the 1S level. When I had finished this work, I thought, the same sort of thing must happen for other atoms, except it's more complicated. One particular case interested me because of my connection with Chandrasekhar, who had many years previously done extensive calculations on the ground state of H-, a two-electron system, on the basis of the earlier work of the Norwegian theoretician, [Egil] Hylleraas, who calculated for the first time with good accuracy the energy of the ground state of helium. Chandrasekhar was aware that there was a small error in the energy that Hylleraas had calculated for He. We did some new calculations, that is Chandrasekhar and I with the help of his computer assistant. This was at that time still with desk computers, not with electronic computers. And we found that Hylleraas' value was certainly off by a small amount. Here in Ottawa I had some help with the computations (but still not electronic computers, desk computers), and we went up to 18 parameters, while Hylleraas' calculation was done with only 10 parameters. I had learned from Chandrasekhar how to do these calculations. The question was, whether there should be a difference between experiment and theory on the ground state of helium, and that was the next thing that I tried to do. The solution to that problem was quite a bit harder than in the case of the hydrogen atom, because the energy interval to the first excited state in helium, instead of being 10 volts, is 20 volts, and therefore the wavelength is 584 angstroms against 1215 angstroms in hydrogen. The problem was again that of standards in that region. I finally decided on Ar+ as my standard spectrum. There were some spectral lines of Ar+ in that region of 584 Å, and the wave numbers of these argon lines could be built up by the combination principle from lines in the visible and near ultraviolet regions. It wasn't all that simple; there were several steps involved because the Ar+ level scheme didn't quite fit. I had to use some nitrogen lines as intermediate, I can't remember all the things that I did, but it was quite a complicated affair. It finally did come out, I must say, rather well, particularly since I was able to do both helium 4 and helium 3 and they agreed with one another except for the isotope shift, which can be calculated, and eventually I ended up with a value for the Lamb Shift in the ground state of helium, of 1,2 cm-1. This Lamb Shift is very difficult to predict. It was done, but it isn't yet certain, I think, whether the calculation or the experiment is better. But the difference is small. I should perhaps say that this work on helium was actually done with the three meter vacuum spectrograph, before our ten meter vacuum spectrograph was built or completed, and what I would have liked to do but never managed to do is to repeat this work on helium with the ten meter instrument, and see whether I cannot improve the accuracy of the Lamb Shift. And of course the calculated Lamb Shift depends on the method of calculation as well, and there was an interesting story because one of the people working with me (J.F. Hart) had done calculations, one step better than we had done by desk computers. He had worked with electronic computers now, up to 24 parameters, and there was a logarithmic term in there that he had added, but it didn't make too much difference. And then Hylleraas came along and he wanted to restore his reputation as a computer of the ground state of helium, and he did the calculations with 24 parameters, and again he got a different value from the one that we got, and again it turned out after a while that he had made a slight mistake in simply transferring one set of numbers to the next sheet, and so the calculations now agree on the value for the ground state of helium. But there hasn't been very much activity in recent years, because everything depends now on a good experimental determination of the energy of the ground state of helium, and the only way to do that is to measure the line at 584 angstroms with higher accuracy.
There's still the problem of standards?
There's still the problem of standards, and nobody has done that yet. Maybe I should do that instead of chasing subjects that probably won't work! I'll think about that. Because the 10 meter vacuum spectrograph is still operating.
We have one more Lamb Shift paper here.
Oh, lithium, yes. That was with H2. Yes, that worked out. That concerns the 2S state of Li+. The ground state we haven't really tackled. That's another thing one might do, but is it really worth all that effort? That is the question. But for the work on lithium 6 and 7 we had separated isotopes. I really have forgotten now what the principal results were.
"The work on this problem was terminated because other more precise ways of checking the results of quantum electrodynamics are now available." (Quoted from Am. Rev. Phys. Chem. 36, 1-30 (1985) p. 23).
Oh yes. But the ground state of helium, I think, and for that matter the ground state of lithium plus would still be a problem that cannot be done by any other method than measuring such a big interval with sufficient accuracy that the Lamb Shift comes out. And of course the calculations have to be done correspondingly accurately.
But maybe that's for the next generation to do. [Break]
I thought I would tell you about the diffuse interstellar lines and the interest I had in them for many many years. Many other people of course have been interested in that question, but it seems to me at this point in time nobody has really come up with a convincing explanation of these diffuse interstellar lines, and they are something very real. When you look at a spectrum of distant stars, you see these diffuse lines, the most prominent one being at 4430 angstroms, but there are a number of others at longer wavelengths that are sharper than the 4430. As I said, many astronomers have talked about these lines, and they intrigued me ever since I became interested in the sharp interstellar lines which fortunately were identifiable fairly easily. In fact, I might mention in addition to what I said about the identification of CH+, the whole paper that we wrote about that didn't take more than a couple of weeks or something like that. It just worked like a charm after I came back from this meeting at the Yerkes Observatory, and the discussions with Teller and Mulliken and others. Following that I thought I could do a similar job on the diffuse interstellar lines, but it didn't work that way. It's now some 20 years or so that I have been interested in them, and I'm still not successful in understanding them. But one of the things that I felt fairly strongly about, and still feel strongly about, is that these diffuse lines must be due to some interstellar molecule or molecular ion or radical.
You mean a single species?
A single species. That's my idea. The astronomers have always started out with the assumption, that it must have something to do with a solid, the interstellar dust or interstellar grains. And I somehow find it difficult to believe that, and I have not seen a really convincing explanation on that basis either. So I started from the other end, from the free molecule or molecular ion picture. In that connection I did some experiments, and spent quite some time in the laboratory, with the help of Mr. Shoosmith, to see whether we couldn't get some absorption spectra of molecular ions, the point being that if they were neutral molecules, surely we would long have found out what they are, because all conceivable neutral molecules are easy to produce in the lab, but it's a different story if you have free radicals or ions, which are not very stable in the lab but would be much more stable in the interstellar medium. So I concentrated on that approach to the problem of the diffuse interstellar lines. Now, one idea that I had was that since CH4 is a fairly abundant molecule in planetary atmospheres, in the atmospheres of the outer planets at any rate, would it have something to do with CH4? It was clearly not CH4 itself, but what about CH4+. And then I thought, yes, if you take one electron away from CH4 you have a configuration similar to what you have in CH3, which has one outer electron (a2") and if an electron is taken from inside to this outer electron shell, you would have a spectrum similar to the one that you would have expected in CH3. Although this state has not yet been found it should surely exist and lie fairly low, and its analogue in CH4++ should be accessible. Anyway, we developed the technique of flash discharge (rather than flash photolysis), in order to catch the ions, and that is rather more difficult it seems, in some cases, than the flash photolysis. This is because the concentration of ions is never very high. So we tried with a simple case, that is the absorption spectrum of flash discharges in nitrogen, because the emission spectrum of N2+ is very well known; the ground state is known, the first excited state is known, and so I knew what to look for. Nobody had seen at that time the absorption spectrum of N2+ only the emission spectrum. And I was successful by this technique to find the absorption spectrum of N2+. Nothing new came really out of it, other than an absorption spectrum was found.
Of an ion.
Of an ion. I think it was the first absorption spectrum of an ion in the lab. I'm not 100 percent certain about it. Anyway, I felt like it. And so then we proceeded to try CH4, in the same way as we did for N2; we should find the absorption spectrum of CH4+. Nothing doing! We found a spectrum, but this spectrum at first glance immediately showed us it wasn't CH4+. CH4+, even if it were a tetrohedronal molecule (which probably it isn't), it would not show a simple P and R branch in the spectrum, without a Q branch.
So it was something diatomic.
It was something diatomic easy to analyze. It so happened that Professor Lagerqvist from Stockholm was here at the time. He was very well versed in the analysis of diatomic spectra, and I asked him to check my analysis and perhaps to evaluate an independent set of the constants, so we decided to join forces and publish the analysis of this spectrum together. It was certainly a new spectrum, but what was it? We couldn't really quite decide whether it was a doublet or singlet. The lines looked like singlet lines, but one thing was very clear, alternate lines were missing, and so it was a molecule with two carbon nuclei. But it certainly wasn't ordinary C2, because we knew the absorption spectrum of C2. The most obvious assumption was that the spectrum belonged to C2+. But it didn't fit in with the predicted energy levels of C2+. So I had the at that time crazy-looking idea of C2-. My argument was, it's in a region very similar to N2+, the same number of electrons, and it's a very similar kind of spectrum and all that. But I had a hard time persuading my co-author, Lagerqvist, that this was so, and the rest of the people in the lab seemed to think I was a little off my rocker or something. A negative ion, good God!! So the title of the paper was not "a spectrum of C2-", but it was "A New Spectrum Associated with C2." But it was mentioned in the text that it might be C2- which it turned out to be. It was confirmed beautifully by Lineberger and Patterson at JILA in Boulder by laser two-photon ionization of a C2- beam. Some more work has been done on that system, not here but in other laboratories. In fact, Takeshi Oka for example has observed the inaudible] a doublet pi system, the analogue of the red bands of N2+ [inaudible]. But at any rate, the first observation of that ion, the first discrete spectrum of a negative ion, was that of C2-. Well, that didn't explain the diffuse interstellar lines, of course.
Not at all!
But we went on. For example, we looked for NH44+, and we didn't find anything. I really thought also of NH4 (neutral) because NH4 is similar to sodium, therefore it must have absorption in the region of the sodium lines, in that general area of the spectrum which fits the diffuse interstellar lines. But of course, that spectrum was found later right here in the lab, and indeed it is in that region and very similar to the sodium lines. But it isn't the diffuse interstellar lines. And there were one or two other things we tried. Of course, I didn't work on that topic all the time, because it was a rather disappointing kind of activity, when you never get anywhere. But recently, more recently, I had an idea for still another ion. I thought I would look over the photoelectron spectra of various molecules. The photoelectron spectra tell us the energy levels of the ions. In looking at the photoelectron spectra of a number of molecules, I found that the formic acid molecule has a photoelectron spectrum where there are at least two intervals that fit the principal diffuse interstellar lines. That is of course a fairly long shot, it may be a chance coincidence; the coincidence isn't that accurate because the photoelectron spectra at my disposal were really not all that precise, or accurate. I asked Professor Walther and his associates at the Max Planck Institute for Quantum Optics about the possibility of looking at the absorption spectrum of the HCOOH+ ion with some laser technique. So one of the students spent some time on looking for the absorption spectrum of the formic acid ion, in order to find diffuse absorption bands. There was some slight indication, but it never worked out, and I think one has to give up that possibility, but for a while I was really quite keen on that, and it seemed rather promising. Of course this has to be compared with the other group of people who believe that it has something to do with a solid consisting of polycyclic aromatic hydrocarbons. PAH's. Either the PAH's themselves or their ions. I find it very hard to believe that such a complicated thing could give such a reproducible spectrum. They think they have proven it, but in my opinion they haven't. I don't believe it. But I may be wrong. I don't know whether I will have another idea; if so, I will certainly pursue it.
I don't think they've proven it yet, either. There's still room for good ideas there, from the discussions at the Brioni meeting (September 1988).
At the Brioni meeting, oh, you were at the Brioni meeting?
Yes. PAH's were very big there. But I would not say there was unanimity around that.
I think they're far from a conclusive proof, myself. It's a possibility. It may even be an interesting possibility. But I don't think they have come anywhere near a proof of that kind of a system.
I believe that at the moment, the hypothesis is, just as in some of your work, stimulating some very interesting research which will bring interesting results about the PAH's, whether or not they bring results about the interstellar medium.
OK. Yes. I certainly accept that. Yes. Anyway, that was my experience about diffuse interstellar lines, and the associated observations of C2-.
This led to some of your very interesting ion work.
Yes. That got me involved in ions, at any rate, and I'm still very much interested in ions.
Was that about the time that the Kouhoteck spectrum was observed?
Oh yes. And that would fit in, although it had nothing directly to do with the diffuse interstellar lines. But as one of the ions that would be interesting to try, I suggested to Hin Lew to look at H2O+. He had a very nice apparatus to study the spectrum of such systems, and just almost the first time trying, he found this new spectrum in the visible and very near infra-red which turned out to be the spectrum of H2O+ And then about a year or so later, I had a letter from Wurm who was a German astronomer who had worked a lot on comets, and an Italian astronomer, Benvenuti. They included a preprint or proof copy of a paper in which they had observed the spectrum of Comet Kohoutek, and had found two doublets in that spectrum. They asked me, what do you think it is? And this just happened to be the time when Hin Lew had found his spectrum, and we looked at his identifications. He had analyzed the spectrum, with the help, incidentally, of the NH2 analysis of Ramsay and Dressler which is a very similar transition. We found that these two doublets were precisely the lines that would remain at low temperature of H2O+. And then a few weeks later I had a telephone call from Dr. Wehinger at the Wise Observatory, right in the middle of the Sinai Desert. He said that he and his wife (S. Wyckoff) had found 25 lines in the spectrum of comet Kohoutek, which they could not identify. He gave me the wave numbers of these lines over the telephone.
Wehinger and Wyckoff?
Husband and wife. Every one of these 25 lines was on Hin Lew's list. So we published a preliminary note that H2O+ was identified in Comet Kohoutek. Later we got together with Wehinger, Wyckoff, Hin Lew and Herbig at Lick Observatory to write a joint publication on H2O+ in comet tails. The presence of H2O+ was, of course, not very surprising because it was generally assumed that there is a lot of water in the heads of comets, that is a lot of water ice, which evaporates as the comet comes close to the sun. The H2O is then photo-ionized by solar radiation, and you get your H2O+ in the tail. So that was quite an exciting little trip outside what I was working on.
Hin Lew got this spectrum just in time, really.
Just in time, yes, that's right. So that is the story of—
—the interstellar problem, the cometary lines, yes. Should we go to hydrogen?
Yes, let's do that.
Perhaps we should discuss the hydrogen molecule before we go to H3.
Yes, I think that would be a very sensible procedure. Of course, I had been interested in molecular hydrogen right from the beginning, when I worked with this PhD candidate Miss Blumenthal, and we had both spectra, the atomic spectra and the molecular spectra. I was, shall I say, fairly familiar with the literature on molecular hydrogen spectra, and I have remained interested in that most of my scientific life. I don't really quite know now where to start on that. Of course, the real start on molecular hydrogen came when I observed the quadrupole lines, while at Yerkes Observatory, and then there were other pieces of work on molecular hydrogen. For example, we did one experiment, before the quadrupole lines were observed in absorption in Jupiter. There was a line in the spectrum of Uranus, a diffuse line, 8270 angstroms. At that time Harry Welsh at the University of Toronto worked on the pressure-induced spectrum of hydrogen. He and his students found that they could get the 1-0 band, the fundamental, so to speak, of molecular hydrogen, in the infra-red by observing the absorption spectrum of molecular hydrogen at high pressure; this was the pressure-induced spectrum. And they also looked at the overtone around 8000 cm-1 and it struck me that this spectrum at 8270 Å (i.e 12189 cm- 1) in the Uranus spectrum would fit with the next overtone, the second overtone of this pressure-induced spectrum of hydrogen. So we did some experiments here with a long 2 meter absorption tube which was dipped in liquid nitrogen to look at the absorption spectrum of hydrogen under high pressure, not very high, 10 atmospheres or something, and at liquid nitrogen temperature, and lo and behold, we could find this particular feature at 8270 with a few other things which I don't want to bother explaining. And this in a way was the first detection of molecular hydrogen in the outer planets, that is, in this case in Uranus. It was only after that that the quadrupole lines were detected by the astronomers in the spectra of Uranus as well as, of course, of Jupiter, Saturn and Neptune. So that was one phase of the work on hydrogen, and then of course we looked a great deal at the emission and absorption spectrum of molecular hydrogen in the vacuum region. Once we had high resolution vacuum spectroscopy established, even before we had this 10 meter instrument, we took photographs of the Lyman bands of hydrogen in emission all the way down from 1800 angstroms down to 1000 angstroms. And I think we made the first reasonably accurate measurements, because previous measurements in the vacuum ultraviolet had all been done in the first order, and they were relying on standards which were very scarce and very far away from one another, and therefore the accuracy of the wavelengths that they obtained in the vacuum ultraviolet was never very good. Why? Well, I don't really quite know why the higher orders were never considered, maybe for lack of intensity or something. The gratings were not properly blazed or what. At any rate, I think our [use of the higher grating orders] was the first, and we got I think fairly good measurements which only quite recently were improved by Isabelle Dabrowski in this lab. But one point was, not perhaps to an outsider a very important point, was that the data that were in the literature, and which Dieke (who did a lot of work on hydrogen), used, were out by as much as 8 cm-1 a constant difference all the way through. I'm still baffled why it should be so much, but in his table of energy levels of the singlet levels of hydrogen, his energy levels of the B state, the first excited singlet state of hydrogen, were all off by 8.5 cm-1. That was one result of this particular work. Then we went to D2 and later we also got to the absorption spectra. In our work on the absorption spectra we were interested in getting close to the ionization potential; that work was done with Christian Jungen just around 1970.
There's one paper just with your name in 1969, "Dissociation Energy and Ionization Potential."
Oh yes, I'd forgotten about that. It was in a way a fairly important paper, since after all the dissociation energy of molecular hydrogen is of course an important constant. It was first determined with any accuracy by Witmer back in the twenties, from the so-called Lyman bands as observed in emission in Ar-H2 mixtures. But then there was Dieke's work on the absorption spectrum of molecular hydrogen, and later Beutler's work on the same absorption spectrum under higher resolution. I continued with the absorption spectrum, at that time with the 10 meter instrument, and I was able to improve the dissociation energy by using low temperature absorption and doing it in H2, HD and D2. That led to a considerable improvement of the dissociation energy of hydrogen. Having done the dissociation energy, I decided that we should also do the ionization potential, and that led us to the study of the Rydberg spectrum and of course Christian Jungen was very prominent in the analysis of that spectrum, which was finished around 1970 and published 1972.
Yes, "Rydberg Series and Ionization Potential of H2."
That's right, that's the paper. Well, that paper was actually finished, just before I got the prize, and it was a good thing because after that I didn't have much time to do anything.
So there is quite a hiatus in my publications after that paper.
I don't think it's so noticeable.
And of course we're still working on molecular hydrogen, particularly again with Christian Jungen we got the 5g-4f transition, the high Rydberg transition, in the infra-red emission spectrum. In fact, when I was looking for H3+, in emission, I found this group of lines around 2500 cm-1, and wondered what it could be. We finally established that it was due to a Rydberg-Rydberg transition of H2 analogous to the first line of the Pfund series of atomic H. In fact, the paper we are working on right now is the paper of the next member, 6h-5g. This work is taking a long time because both Christian Jungen and I had other things to do, and there were other difficulties. Anyway, all I'm saying is that we're still working on hydrogen. Oh yes, there was one other interesting event. We were looking at these infra-red spectra of a discharge in hydrogen, and I had a call from Takeshi Oka. He said, "Have you seen this paper reporting a new laser line in the infra-red of hydrogen?" I said I hadn't, and I looked at it, and it turned out that this laser line was on our spectra and it belonged to a transition between the first two excited electronic triplet states of hydrogen. Well, we contributed to the interpretation of this spectrum and other people have worked on that spectrum recently, so it was quite an interesting occasion to see some more spectra in the infra-red. We were looking for H3+ but we found these new spectra of the hydrogen molecule! The H3 of course we found later, in the infra-red, at first, anyway. H3+ of course was found in absorption by Oka in 1980. Actually H3 was found a year before that, 1979.
I'd forgotten that you got that before Takeshi found his lines.
That is right. It was a case of serendipity if you like. We weren't looking for H3. We were looking for H3+. And we were looking in the infra-red, and when we had, for example, this 2500 cm-1 group which at first we didn't know what it was, it might have been H3+ thought we should look at the visible spectrum of hydrogen in the same discharge in order to establish what the temperature really was in this discharge, not by measuring with a thermometer but by looking at the rotational distribution in the hydrogen spectrum. And then I left for a trip to Moscow, and asked Hurley, the successor of Mr. Shoosmith, to get some spectra, while I was away, of the visible spectrum of hydrogen, in this very discharge that we had used for the search for H3+. And when I came back he put two spectra on my viewer here, in the back of the office, and he said, "That's what I got. I don't understand it." And I didn't understand it either! And here were a number of diffuse lines, nothing to do with the diffuse interstellar lines unfortunately, and what could they be? And I think for about a week or so every day I looked at the spectrum and thought, what has he done now? Some stray light coming into the spectrograph or some crazy thing like that. But it was a little too regular, and the regularity was particularly striking in the spectrum obtained with deuterium, but there was also something in the case of hydrogen. Well, I took a ruler like this, and measured the spacing of the lines in the spectrum, converted it to reciprocal centimeters, and found that the spacing in the spectrum obtained with deuterium was 44 cm-1, and if it were a diatomic system, that would correspond to a B value of 22, and the B value of D3+ predicted at that time, not yet observed, was just around 22. I thought, it can't be H3+ because H3+ was not expected to have a low lying electronic state, for one thing. Not that low, in the visible, in the red part of the spectrum, 5600 angstroms. And on the other hand, when I measured in the hydrogen spectrum, the spacing was twice that. So there was some relation here. And I worried about that for a couple of days, and then it suddenly struck me, if I had a Rydberg spectrum of H3, not plus but neutral, then in the Rydberg spectrum the B value would be very similar to that of H3+ or D3+, whichever the case may be, and therefore it seemed reasonable that because the ground state of H3 was surely expected to be unstable (that much I thought we knew from theory for certain), it couldn't be a stable state, but the Rydberg states could be stable.
And would have the low energy interval.
And would have this particular energy interval, the B value of 22 for D3 and 44 for H3.
And could fall in this 5600 angstrom region.
And could fall in that region. 5600 is not very far from the H alpha lines so it could be the corresponding kind of transition. At that stage I felt really sufficiently convinced that I thought, now, I must try that on Alec Douglas. I went over to his office, and he thought about it and said, "That sounds good." He agreed. Then I knew I was right.
That sounds like a good test.
Well, to complete the story really I should mention about H3 that in addition to this diffuse line band that was the original observation (and I'm still baffled why nobody in 50 years of the study of the spectrum of molecular hydrogen ever saw that, never mentioned it in any of the papers but that's another question), we did then find some other lines, which were not broad, and which also belonged to H3, and they should have been seen in, for example, in Dieke's book on just the whole set of lines of molecular hydrogen.
This is in the visible?
In the visible region. Why did nobody see that? I don't know. Anyway, we found for example another band at 7000 Å that was a perpendicular band. The first band we discovered was a parallel band. But we also had at 6025 angstroms another band which was quite sharp in D3, with P, Q and R branch. The P and the R branch and the Q branch were resolved with all the K structure and everything, so that there could be absolutely no question if anybody wanted to doubt that this was H3; we had everything. And then of course we had one other band there. It was also sharp, but it was very complicated, because it was a mixture of a number of electronic transitions. This band together with one infra-red band was analyzed by Jim Watson and Jon Huygen. In addition there was a nice sharp infra-red band near 3600 cm-1 which was analyzed more easily because it was much less perturbed. So it was really quite a complicated and extensive spectrum that eventually showed up, and the end is perhaps not yet in sight. ... actually now we have spectra of the various isotopes, H3, H2D HD2, and D3. Looking at the difference in line width, in the sharp band at 6025 Å, we find that the line width increases with the J value, and in H3 only the first lines are reasonably sharp and then they become very diffuse like the lines of the 5600 band. So we are now trying to establish the line widths of the various isotopes and their variations with the J and K quantum number. That is I think the main activity in that area.
These are pre-dissociation line widths?
Pre-dissociation line widths. Pre-dissociation in the lower state. We can't really have pre-dissociation in the upper state, because then you wouldn't see the lines. They wouldn't emit. So it's all in the lower state. Anyway, all I'm trying to say is that we're still working on H3 and D3 and H2D and HD2.
The isotopic species will present some complexities, I'm sure.
Yes. It's not all that trivial because they are asymmetric tops. H3 and D3 symmetric tops, but H2D and HD2 are asymmetric tops.
So we're getting some experience. That's, I think, all I can say about the H3 problem. But in connection with that, I don't remember how I came to look at NH4 again, but I knew of the work of Schüler and his people on the spectra obtained in ammonia. That is, if you send a discharge through ammonia under suitable conditions, you find the Schuster band of ammonia near 5655 Å. Schuster was a German physicist who went to England, to Manchester, and stayed there, and was accepted as a Britisher. He had published a short notice in which he described a feature in the spectrum of a discharge in ammonia. That has been known for 50 years, and the question really was, what was it? And then Schüler and his collaborators studied this spectrum and found some other similar features. In fact, they even observed the isotopes at the time; this was around 1958. And the question still remained, what was it? Somehow or other, I became interested in these spectra. It struck me that it was in a way a rather similar situation to that of the H3 spectrum. H3 was at 5600 Å, the Schuster band was what, at 5655 Å, but there was another band that Schüler and his people found which I call the Schüler band (6747 Å in NH4 6535 Å in ND3. It was even more striking. It had a doublet structure, and that reminded me of the fact that if you had NH4 or ND4, you have an outer electron. You have a structure similar to sodium. And therefore you should see something similar to the sodium D lines. And here was a doublet of the same order of magnitude, but it was a band, each one was a branch. Not a very clear branch, mind you, a rather complicated spectrum. And the idea presented itself to assume that it was again a transition, a Rydberg-Rydberg transition, in a system where the ground state was unstable.
Analogous to the H3.
Yes, analogous to the H3. Then Jim Watson came into the picture, and tried to model a band of this sort, and pretty soon he had an analysis, that is of the Schüler band, but for the Schuster band we got it wrong; it turns out that apparently the Schuster band doesn't really belong to this species, but belongs to a system of ammonia itself, NH3 rather than NH4.
Oh, really? I hadn't caught that part of the story.
Yes. Well, actually there is a paper in the literature by Jon Huygen and myself where we still thought it was NH4. And we analyzed it in those terms! But there are some people at IBM, whose names I don't recall, and Jim Watson from our lab who showed that it's pretty certain that the Schuster band really is a spectrum of NH3, and has nothing to do with NH4. But NH4 has a fairly extensive spectrum. There was also some recent work done at the Max Planck Institute in Garching in which they have studied spectra of H3 and NH4 with their laser methods. They had a beam of H3+ and they sent it through a cell containing cesium vapor or sodium vapor or whatever, and thereby discharged the H3+ and got neutral H3. They observed in this way the same spectrum that we had, but under fairly low resolution. They did quite a lot of work on H3 and D3. It supplemented what we were doing; they could determine the lifetimes of the upper states and all that. It was very interesting kind of work. They applied the same method to NH4 and ND4, and they observed the Schüler band. So I think everything is well taken care of there, and the ND4 is the sharp one, again, and NH4 is more diffuse but still recognizable. But I don't think it has ever been analyzed in detail. At any rate, the ND4 has been fully analyzed by Jim Watson.
Have you been tempted by CH5?
Yes, I have been tempted. Yes, indeed I have. And we tried, but we didn't get anywhere. It's a good point, yes.
Other people have been tempted too, and I couldn't resist asking.
Yes, there should be something similar. We have also been tempted by H3O. Or D3O. And I don't know whether the end of that story is there, but so far we haven't found anything that we can pin down. We might come back to it.
No electronic transitions?
Not so far. I mean, it should be very similar to NH4, you see. Except it doesn't quite have the symmetry. I mean, the NH4 really has tetrahedral symmetry. That doesn't help for the analysis, but it does follow from the modeling of the ND4 band that was done by Jim Watson.
OK. And the H3O would have to be planar or pyramidal of course.
Yes, just like ammonia, if you like. So that is still to be done.
Well, then I think you still have something to do.
Now, was there something else that we wanted to talk about?
Those were the molecular subjects actually that were most important.
When I arrived in New York, one of the first people that I met was Harold Urey. He was then at Columbia University, and he was already fairly well known. Oh yes, it was after the discovery of heavy hydrogen, so he was very well known. I mean, it was 1935, and the discovery of heavy hydrogen was '32.
Yes, and you had already made heavy acetylene etc.
Yes, that's right. Anyway, Urey was very nice to me, very hospitable. I was in his house and so on, that is, both my wife and I, we met the Ureys. At any rate, he gave me a manuscript to referee, because had just started being editor, the first editor of the Journal of Chemical Physics, and I looked over this paper as soon as I got to Saskatoon. I don't think I did it on the trip yet. But I wasn't terribly enthusiastic about that paper. That's what I've been trying to remember. I had some criticism of that paper, which I don't think I wrote down in my review. Anyway the paper was published. And I never thought of it any further, until I found out that the author, P. Flory, became very prominent in macro-molecules, and indeed later got the Nobel Prize. I met Flory a couple of times, but I didn't refer to this story to him. This was my very first refereeing job, because the papers in the Zeitschrift für Physik, for example, were not refereed.
It was the domain of the editor?
It was the domain of the editor. Scheel, the Editor of Zeitschrift für Physik was a very jovial kind of person (of considerable girth) and if you had a manuscript, you handed it over to him by hand, he put it in his pocket, and some time later the paper was published! In fact just in a recent letter I pointed out to the editor of the Canadian Journal of Physics, because they asked me about what the method of refereeing should be—should there be two or even three referees? All this kind of thing, you see. And I said as a rule there shouldn't be more than one referee and then I mentioned the fact that in the Zeitschrift für Physik at the time (the early thirties) that all these famous papers of Heisenberg and others, were published, there was essentially no refereeing as far as I could detect, because right next to a paper of Heisenberg was a crackpot paper.
Oh, so it was a very generous selection policy.
A very generous selection policy. And I didn't think that it hurt the Zeitschrift für Physik if there was once in a while a crackpot paper in it. I made that remark to our editor of the Canadian Journal of Physics. And I still maintain that that is so. Of course, if you are limited in space and so on, it's a different matter, but I find that sometimes refereeing is overdone. I also mentioned the fact that I heard a story of Einstein, when he came to this continent from Europe after the Nazis appeared on the scene. He submitted a paper together with some others to the Physical Review, and he was very upset when there was a long delay in the publication and some criticism of the paper of Einstein!! And my feeling was, so I said to our editor, that if a person like Einstein submits a paper, it should be published, no matter how nonsensical it is. I didn't put it that way. I mean, he should have the freedom, in other words, to publish what he thinks is right. And it should not be criticized by referees. Of course, if he wants refereeing, I mean, if he says, "I'd like to have an independent opinion," that's a different matter.
Entirely different. But you have served as a referee.
I served as a referee many times after this first paper in the Journal of Chemical Physics, and of course many other journals, like the Canadian Journal of Physics.
Yes, these journals are listed here somewhere. Astrophysical Journal, you were on the board.
Yes, I have refereed for the Astrophysical Journal. Not all that many but I have refereed there.
Being on the board of that also involved mainly refereeing?
Were there meetings of the editorial board?
Practically not, I would say. I can't remember one but there may have been one, I don't remember. And of course, I am still on the board of the Journal of Molecular Spectroscopy, which of course now is really one of the dominant journals, particularly in infra-red spectroscopy, but also ultraviolet spectroscopy. And I find, for example, in the revision, that more than half the modern references on a given molecule are in the Journal of Molecular Spectroscopy. 40 percent of the remaining 50 are in the Journal of Chemical Physics. This is rather fortunate, because I can just get up here and pick it up from my shelves. If I had to go to the library every time I needed a reference it would take much longer. But I was really amazed how many are in the Journal of Molecular Spectroscopy. Even though it's published only once a month.
This has come to dominate over the last twenty years.
Of course at the time you arrived, say, in Saskatoon, a lot of the spectroscopy could be found at that time in Zeitschrift für Physik?
And what about the American spectroscopists? You found these in Physical Review?
Physical Review, oh yes. Particularly before the founding of the Journal of Chemical Physics. And even after that, many papers, for example, Mulliken's papers were published there.
Urey's papers certainly were still in Physical Review.
Yes, in Physical Review. Those were really the papers. Now of course there are many more journals and it's almost impossible to really get through the Journal of Chemical Physics with any kind of depth at all. I mean, I practically spend every Sunday to look over the Journal of Chemical Physics, and the Journal of Molecular Spectroscopy. Those are the two that I make it a point to go through carefully each time. I don't read all the articles. I couldn't do anything else then.
No, that's right.
But I look at the titles and look at the abstracts if I find it interesting. Sometimes, perhaps one paper per issue, I read.
The Canadian Journal of Physics, you're listed here as an associate editor some years ago.
You probably were associate editor for quite a few years.
Yes. I still am.
You still are. OK. Well, are there board meetings for this journal?
No. As you know, the Journal of Molecular Spectroscopy now has three people who are really more closely associated with the editor. The rest of us are still named on the cover, and we still get the Journal of Molecular Spectroscopy free of charge. That's the most important point.
Yes. As Manfred (Winnewisser) is one of those I'm fully aware of this.
It helps greatly, because it's quite expensive if you want to subscribe to it.
Well, that's the reason why we don't have it anywhere else in the university.
Is that right?
The physicists had it but they gave it up some years ago.
Oh dear. We have two, we have my copy and there's a copy for the general use outside in the other room there.
And you can send them to the bindery staggered.
Yes, that's right. But Physical Review, Journal of Chemical Physics and Astrophysical Journal certainly were journals where I served on the editorial board or whatever they call it. But not more than once in each case.
You mentioned that there was a meeting that you maybe had trouble getting to. How did you get travel funds when you were in Saskatoon? How frequently did you come to meetings in the United States?
Well, at that time of course one didn't travel by air. One traveled by train. And train travel was reasonably cheap, I would say. At any rate, I don't really remember any problem of that nature. I paid it out of my own pocket! Well, most of the times I was in Saskatoon.
How often did you find it important to go to meetings, approximately once a year?
Once a year. I certainly didn't go more often than once a year, even for financial reasons. And I had a family growing up. I didn't want to be away for long.
You have mentioned several visits; this meeting in '37.
This meeting in Princeton. That was a very very fine meeting on molecular structure and molecular spectroscopy. Some of the top people in the field were there, Mulliken and Wigner and other people, Kistiakowsky I met for the first time there. It was really for me the first really impressive meeting on this continent. And it was not so big that one got lost.
About 80 people or 100?
Well, I would say it was more between 100 and 200. It was a fairly big meeting.
You mentioned Kistiakowsky and that you had tried to do some spectroscopy of detonation effects. Was there any interaction with Kistiakowsky involved in this work?
Well, he was on the same committee that was looking after these elementary detonations. But I don't really remember how often he did attend those meetings. But I did meet him once in a while on that committee. And then of course there was a problem when the war started, and particularly when the U.S. entered the war. I think I mentioned that at one stage when I was down in the States and wanted to come back and I was stuck at the border, they had suddenly closed the border for enemy aliens like myself. Later on I had an "Identification in lieu of a passport." And that made it possible for me to go to these meetings, which were classified meetings, but not very highly classified. I remember at one meeting there was Gamow there with a fancy idea about detonation that would go around a spiral wave and in the center was the big bang then. This kind of thing he was talking about.
This was during the war?
Yes, during the war. Shaped charges and all this kind of thing, that I heard about. There were certain explosives that I was sent when I was in Saskatoon. I made a little hut built of earth, to detonate these, and in a neighboring small hut I had the spectrograph with a mirror at right angles and so on, and once in a while I made a big noise!
You had small samples of various explosives?
Yes, pellets. They were perhaps, 10 grams or 20 grams. Maybe as much as 50 grams.
You exploded them electrically?
Yes. Right. Well, there were these initiators, detonators, yes. Detonators, and they were detonated electrically, and the small detonator then detonated the main high explosive. The detonator was mainly sodium azide or something like that. But the high explosive was something that's called RDX and NENO and I don't know what they were.
You didn't know quite what was in them?
Well, I could have found out, but I was not a chemist.
You were interested in the spectra of the detonators or of the explosive?
Of the explosive, but particularly of the detonation wave and this sort of thing.
Was there any attempt at a sort of time resolution?
Time resolution was there. Yes, I had a rotating mirror in front of the spectrograph, and that was quite elaborate actually and it took a little while to set that up. So I could resolve something of the order of a microsecond. I had a picture of the detonation, and it was bent, the high explosive was in this form, shall I say, and I imaged this detonation wave that was going down there onto the slit of the spectrograph, and then I saw the distribution in time. Well, maybe I'm a little optimistic when I say one microsecond, but certainly ten microseconds was what I could resolve. I published one paper on the subject after the war.
Oh, it was declassified then?
It was not classified, no. It was published in NATURE (vol. 161, 647 (1948)). That's right.
In NATURE? I'll have to look for that. So all the experimental setup and so forth finally at least culminated in one publication.
Yes, that's right. But the results were really somewhat disappointing. I don't think they contributed to the ending of the war.
Well, then, since we were discussing your traveling and these meetings, I wish you would recapitulate some of the l type doublet story.
Oh yes. While I was in Saskatchewan, of course, and in the process of writing Volume II of my three books on molecular spectroscopy, Volume II was on infra-red and Raman spectra, I came across the problem that for example, in a linear molecule, when you have what we call a perpendicular band, there's a Q branch and a P and R branch, and I was familiar with the fact that in diatomic molecules, the Q branch and the P and R branch have different upper states. And I wondered whether this same sort of thing wouldn't happen in a vibrational problem. When you have a degenerate vibration, in a linear molecule, it is really very much like a degenerate electronic state in a diatomic molecule, and the nuclei in the molecule are making rotations, one way around or the other way around the symmetry axis, and that's why there is a double degeneracy, if you like. Of course you can also say it moves in one plane through the internuclear axis or in the perpendicular plane. And I thought and thought about this problem, and came to the conclusion that there must really be lambda type doubling, except it wouldn't be called lambda type doubling because lambda is the electronic angular momentum about the internuclear axis, and here we have a vibrational angular momentum about the internuclear axis. There's another quantum number called l for this angular momentum, which I already knew about, but it must show the effect of this splitting. And then I looked at the spectra that I could get at that time in the literature, and I found that there is really evidence for this l type doubling. For example when you look at the very poorly resolved fundamental of CO2, the nu2 vibration at 667 cm-1. I found that while the P and R branches were clearly shaded to the red, the Q branch was shaded to the violet. I realized that the reason for that was that there was this l type doubling, that the Q branch had in its upper state an effective B value that was a little larger while the P and R branches had in their upper states an effective value B value that was a little smaller than the average value. Therefore the splitting presumably increases in the same way as in lambda type doubling, that is with J(J+1). And I considered the matter further and ended up with a short paper; I sent it actually to Professor Mulliken in Chicago, asking him to present it for me at the first meeting on molecular spectroscopy that was a forerunner of the Columbus meetings that we have had now for 40-odd years every year. At that time, I think they were every second year for a couple of times, and then it finally ended up in Columbus. So at that time then, at this meeting in Chicago, I was not present, partly because I was busy with writing this book, partly because during the war it was difficult for me to travel. At any rate, at this meeting, so I was afterwards told by Mulliken, Harald Nielsen made some remarks on the theory that might be underlying this l type doubling. He worked this out more after the meeting, and there was a remark published together with the publication of the other papers of this meeting in the Reviews of Modern Physics and you could find there that he agreed that there was this l type doubling in the approximations that he was familiar with, but the formula that he and Wave Shaffer, also at Columbus, derived, differed by a factor of 2 from the formula that I had guessed. And they were very insistent. I thought I had a fairly good reason for my formula, but there was quite a heated correspondence, which I still have, between the two of us, and I felt that they were a little, how should I say, too certain of what they were saying, because they felt they were the theoretical physicists and of course I was a mere experimentalist. But one or two years later, they published a paper on the same subject and said that they had made a mistake and that their formula did actually agree with my guessed formula. So naturally I felt rather pleased about that.
So we send our students back to your book to learn about l—doubling when they first confront it, young people that are working on the fulminic acid that I mentioned today. Of the subjects I mentioned, we might as well discuss the Nobel Prize.
I know you've related in some of your biographical comments before that you were traveling in Russia when this news first was announced.
Yes. I think it was probably my second visit to Russia.
You might comment on your trips to Russia.
The first trip that I made was in connection with the IAU meeting that took place in the Soviet Union for the first time, and that was in 1958.
Is this when you were president of the Commission 14 of the IAU?
Not at that time, but at the next meeting in 1961. At any rate I was a member of this commission and the commission was actually meeting in Moscow. There were a thousand astronomers in Moscow at that time. It was a remarkable meeting from that point of view, the first time that such a big scientific meeting was held in Moscow. My second trip was in connection with the fact that I was a member of the executive of the Physics Union, IUPAP. And the president at that time was a Soviet physicist, a very well known Russian physicist, Ioffe. He was a grand old man of Russian physics at the time. He arranged this meeting of the executive in Moscow. That was not yet the trip where the Nobel Prize was announced, that must have been in 1959. It was one year after the IAU meeting.
Were you able to make some contribution, you feel, to the intensifying of scientific contact with the Soviet Union at that time when it was not so easy?
Well, privately, yes, if you like, but not in any official capacity. At any rate, I was asked to lecture in Moscow, whether it was the third or fourth trip to Moscow, in 1971, this was in the late fall of l971, and I lectured in Moscow. I gave two lectures there, I think, and my host was Professor Mandelstam, the son the Mandelstam, who together with Landsberg discovered the Raman effect independently of Raman in 1928. I went then for the first time from Moscow to Leningrad to give another lecture, and there my host was Professor Frisch, a very well known atomic spectroscopist who also wrote a book that is well known in the Soviet Union, of which I have here a copy, on atomic spectroscopy, and we had lunch together. He, Frisch, was called to the telephone while we were having lunch. He came back with the news that there is a rumor, a rumor, that I had got the Nobel Prize. Well, that was quite a surprise to me, of course, and for that matter, I didn't really want to bank on a rumor, but they wanted immediately to have some champagne. But as things were, I had come to Leningrad from Moscow by the famous Red Arrow Train, but although it's very famous, the facilities are not very good, and I decided on the way back I don't want to take the Red Arrow again, I'll just take a daytime train. My Russian host didn't understand why I wanted to take a daytime train when I could travel with the Red Arrow at night. They took me actually to the train station, and put me in my seat, a numbered seat, and then they left me there. The train had still not started but I was sitting down in my seat there, and a man came in and he said, "I'm from the Academy of Sciences, and we've just been informed, and it has been confirmed, that you have the Nobel Prize in physics!" Then he left, and the train left. And here I was amongst Russian peasants, because it was a daytime train, no respectable person would travel in daytime from Leningrad. This was sort of 3 or 4 o'clock and the train was scheduled to arrive in Moscow at 10 or 11 o'clock at night. And here I was for six hours without anybody to talk to, wondering what had happened!
All alone with your thoughts.
Alone, and to believe that it was physics that I got the prize in. I thought there must be something wrong, because, anyway, when I arrived in Moscow, my host, Professor Mandelstam, and his colleague Sobelman were at the station, plus about a dozen reporters, and the secretary of the Canadian embassy in Moscow, and they confirmed of course then that the prize was in chemistry. Indeed, there was a telegram from Dr. Schneider, who was then president of NRC. And so my host said, "Well, you must be very tired. We'll take you to your hotel." And I said, "Well, I may be tired, but I certainly won't be able to sleep." "All right," he said, "then you come with me," you see, and they took me to his home, the first time I'd ever been in a home in Moscow, and we had a party. Champagne and all.
Good. It was more than a rumor this time.
It was more than a rumor this time. Eventually I got back to the hotel. And then of course in a way trouble started, because there was never any rest. I had phone calls from Ottawa, from the radio station in Ottawa and this kind of thing - - or Toronto actually.
How long were you still staying in the Soviet Union?
I think just another two days, something like that. Yes. So it was quite an exciting time. Of course, for a whole year there was no way of thinking really of concentrated work, because there was always something coming in, in connection with the prize, some organization would have a party. For example, the Scandinavian Businessman's Association! And I had to be careful with Scandinavians because they had given me the prize! And things of that sort. So it really was quite a strenuous year. In fact, in the first year I think I had about every day, on the average every day, an invitation for something or other. I mean, to give a lecture here, a lecture there and all this sort of thing. Well, it was certainly exciting and really very unexpected. And then of course in December was the ceremony in Stockholm, which was certainly a very exciting event. Actually the date on which it was announced was the 2nd of November which was rather late because, the then president of the Academy, or the president, or the president of the Nobel Foundation had died and somebody else took his place, so there was a delay in the announcement of the prizes. Usually they are announced some time in October. At the same time, some time in November I think it was, I was asked to give the Linus Pauling Lecture in Seattle. Indeed I have a half-sister living in Seattle, and this was to be on the 5th of December, and the Nobel ceremony was on the 10th of December, but I had already accepted this affair. They gave me the Pauling Medal or whatever it's called, I don't remember, at this occasion, and so I went directly from Seattle, after my lecture there, to Stockholm. I arrived there on the 8th or 7th of December, and of course you are received like royalty, no checking of passports or anything like that, it's done by other people, and you get a chauffeured car and you have a special place at the airport where you are taken first, and so on and so on. It was really quite something. But the ceremony is always on the 10th of December—the anniversary of the death of Nobel.
Oh, that's the reason for the date.
Whether it's Sunday or holiday of any kind, it's on the 10th of December.
I haven't looked at all the dates, but I believe it is following the Nobel Prize, you have a series of publications on science policy, the importance of basic science and so forth.
Yes. Having received the Nobel Prize, it was assumed that I know everything. Whether it's science policy or whether it's something else, it doesn't matter. For quite some time it was quite embarrassing to be asked to so many things where people thought I had the right opinion. So, I was also asked about science policy. In Canada, at that time, we had just a Committee of the Senate. The Senate in Canada is not as powerful as the Senate in the United States. It's not an elected Senate. But at any rate, the Senate had taken it upon themselves to have a committee on science policy, under Senator Lamontagne and they had spread the gospel that science policy is a very necessary thing, and I had the feeling it's not really very necessary and usually the wrong ideas are propagated and so on. So I was quite outspoken sometimes about science policy, already before I had the prize, but after I had the prize of course I had a, as you say in German a "Jagdschein," I could say almost anything I wanted, without having to be so careful as I was trying to be before.
And with the chance that more people might listen to you.
And more people were listening, that's quite right, yes. So there are one or two publications connected with the Royal Society of Canada where I was asked at some of the meetings to say, talk about the needs of science in Canada and this kind of thing.
Yes, "the importance and needs of Canadian research in science", Transactions of the Royal Society of Canada. So it will remain for someone else to see how much effect this has had.
Yes. Now we have of course our most recent Nobel Laureate, John Polanyi, who is a very articulate person and he can express himself far more easily than I can, and does it really extremely well, and he has certainly made comments which I think are not very far removed from what I was saying. After all, all scientists are fairly convinced that you can't direct science, not pure science at any rate. You shouldn't direct science. Nobody would ever have discovered or invented the laser if it had been directed science. It was not because somebody had the idea and told the scientists, "You invent the laser." It just doesn't work that way. But that's what these naive people like Senator Lamontagne and Company seem to think.
Yes. Let's take that lead and go to your invitation to Japan. Were you invited as an advisor to the organization of the Institute for Molecular Science?
Yes. That was one trip. I had been in Japan before, because there was this very big meeting on molecular spectroscopy. It was a very fine meeting organized by Morino and others.
1962? This is when I remember Takeshi Oka saying he first met you at a spectroscopy meeting.
You're certainly right, it must have been in the sixties. At any rate on my second visit I was invited by the people who were planning the Institute of Molecular Science, and indeed I was at that time received by the Minister of Culture and Science for the appointment as a member of this committee, and then I went to Okazaki where the institute was going to be. It wasn't built yet. So I saw the place where it was going to be built, and there was a meeting of the committee under the chairmanship of Kotani. That committee was to establish the policy and to settle a number of things. Of course, the proceedings of this committee were in Japanese, but they asked me to attend one session and give a talk, an informal talk on what I thought would be important in running such an organization like the Institute of Molecular Science. And I talked. I had learned of course very much here in Ottawa at the National Research Council from one of the former presidents, the late E.W.R. Steacie, who was an extraordinarily able scientist, and an able administrator who was able to cut red tape wherever he saw it, and he saw red when he saw red tape! That led of course to the so-called Golden Age under Steacie. He died much too early in 1962. But I had sort of inherited from him the ideas of how to run a laboratory. I emphasized to the committee that one of the most important points is to get good people and let them do what they want to do, not tell them, do this, do that. That is what I learned from Steacie and I talked around this theme for let us say half an hour, three quarters of an hour. I found later when I came back to the institute that they had transcribed my talk, translated it into Japanese, and I think they gave me a copy of the Japanese version of my talk. This was many years later, and it had been handed over to many of the people on this committee and other people involved with the founding of this institute. I found then that they had to quite an extent followed a policy that was very similar to what I described as being the policy of Steacie, as having been successful at the National Research Council. I was quite pleased with that. Whether I had really any influence on it, I don't know, but the fact that they still had the transcript of my talk shortly after the founding of the institute, caused me to believe that maybe it had some effect.
I can well believe it. We visited the institute once and what we saw and in particular in the fact that Hirota was not bogged down with administrative duties, he was doing science, I saw some echoes, I believe.
Yes. And of course I visited the institute on a number of later occasions, when the first building was built and there was a meeting there and I attended the meeting, and they paid my way over from Canada to Tokyo and so on. And the last time I was there was only the 10th anniversary of the starting of the institute; they celebrated this 10th anniversary. And invited me to be there.
That's very nice.
That was really very nice. The first director of this institute was Akamatu.
He retired I think just about at the time of the 10th anniversary, and the next director was Nagakura. He later moved up to be the director of the whole group of institutes that are around there in Okazaki, there's the Biological Institute and still another one, but now just last year, he got the job of founding president of a new university which is entirely a graduate university or institute of advanced studies ... or something like that. That is now being prepared. He's still in Okazaki.
Just one question—in your remarks about the structure of the institute, did you mention library facilities? Do you remember if this was a point you mentioned? I'm asking because I noticed the one time we were there that they have a fantastic library for such a new organization. They would not have to be advised by you, of course.
No. I don't recall that that was a special point in my talk. No, I don't recall that. It probably wasn't.
Something they knew well enough.
They knew well, yes.
This question comes from my German orientation, because the university libraries in Germany tend to be very mediocre even today.
You mean they were mediocre before?
Well, they were when I first came to Germany.
Is that right?
That's not very long ago, by the standards of our discussion this week, but they do not compete with even Mississippi State University, the library and its organization.
Is that right?
Any major university in the United States has a better library than its equivalent in Germany.
Is that right?
There will be subjects of course where some professor at some time made sure they have a complete collection and the right journals, but it's very spotty.
That's interesting. I didn't realize that. But nowadays of course libraries have a hard time keeping up.
Nowadays of course there's a crisis approaching even for American and Japanese.
It's a real crisis, I think, because the journals are getting so expensive. I'm shocked when I see the prices of the Journal of Molecular Spectroscopy, that a regular subscriber would have to pay. Or the price of the Journal of Chemical Physics. Fantastic, if you're not a member of the Physical Society.
How much interaction have you had with your colleagues in Germany since the war?
Since the war? I think I have had a very considerable amount of interaction. It was in a way started by one of our first postdoctoral fellows from Germany, who was Peter Brix, who at that time was actually taking a job in Darmstadt. He was a student of Kopfermann in Heidelberg. And later he went to the Max Planck Institute for Nuclear Physics in Heidelberg. Gentner was there and other people. At any rate, Brix was the first who came over here. Since that time we've had a fair number of postdoctoral fellows from Germany, including Giesbert (Winnewisser). But quite a few others I would say. That is one side. I traveled back to Germany for the first time in 1950. My brother of course was in Germany. He was not affected by the Nazis in any direct way. It wasn't yet so that a person is persecuted because his brother had left the country or had married a Jew; it didn't quite go that far, so he had no particular difficulty, and indeed I think his mother-in-law was quite a bit infected by the Nazis, so I gather, but I didn't inquire into that particularly. At any rate they survived in spite of the bombing of Hamburg. That was the first time I visited again. It reminds me for a moment of an occurrence. I was asked by the radio people here, to take part in a memorial session for Röntgen, it was the 100th birthday of Röntgen or something like that, shortly after the war. They wanted a transmission from Canadian radio in German to Germany, and asked me whether I would do that, and I did. It was a very short thing. But it so happened that was the first time that my brother heard of me, actually a live voice, you see. One didn't think of phoning over there yet or anything of this kind. The amusing thing was, he wrote back that I sounded like an Englishman who knows German very well! Anyway, what I really wanted to say, I then came to Germany in 1950, 1952, 1954 and so on, and I had many connections with German physicists in particular. I had in many ways a somewhat similar activity as I had in Japan, in that I was asked to be a member of the "Beirat" of the Max Planck Institute. At that time it was just the "Laser-Forschungsgruppe" that had been set up by the Max Planck Society and the Ministry for Research and that had been set up for five years, and I was on the first committee, and still am on that committee, which is now the committee for the Max Planck Institute for Quantum Optics. The committee didn't have much to do with the founding, but we were always called to give some advice in a small way, you might say. Anyway, that established my strong connection with the Max Planck Society.
The "Beirat" makes some decisions or contributes to decisions on which research projects within the institute will be funded?
No, it doesn't go that far. Fortunately. All it does is really make recommendations to the president of the Max Planck Society about the work of this particular institute for which it is the "Beirat", and the president of the Max Planck Society refers these recommendations to the directors of the Max Planck Institute, and the directors of the Max Planck Institute take note of these recommendations, but don't have to follow them. And I think that's a very enlightened attitude toward this kind of Beirat or committee that gives advice to an institute. I mean, there have been instances where the "Beirat" has said, "Well, we don't really think that this will go very far" or "We don't think the institute should spend much money on this particular project" or some such items were in the report of the "Beirat" to the president. But there was never any difficulty, because the directors have the power to accept or not accept that advice. I find that very good. So that was in a way my main connection with German science. There was an international meeting in Hamburg, a meeting on vacuum ultraviolet spectroscopy and associated things, and I got an honorary degree from the University of Hamburg at that time. That was for me, being a Hamburger, a special occasion. We were staying at the place reserved for the visitors to the Bürgermeister, and this kind of thing. It was quite a nice occasion. I also had a connection with a physical chemist in Frankfurt. He was here and spent some time here actually, and he arranged for an honorary degree for me in Frankfurt, but even before that, earlier than that, the first honorary degree I got in Germany was from Göttingen, with which I'm very pleased, of course. It was arranged by, you know Lüttke, the chemist. He was originally a student of Mecke. I knew him from that time, and he was then dean in Göttingen. In fact, he's just retiring now. He was the one who arranged this "Ehrendoktor" in Göttingen. And of course I gave a lecture in Göttingen in the place that I knew, the same place where I had heard Franck and Pohl and these people; same lecture hall, and Pohl was there at my lecture, Pohl of course was known for the quality of his lectures, a brilliant lecturer for the elementary classes, and I think I learned something from him. So he was quite pleased!
You told him that you thought you'd learned something from him?
No, I don't think I did, no.
He could still be pleased by the results.
So I think that's all I can think of at the moment about my connections. Oh yes, I think I told you also about my visit with Lüttke to the little town of Herzberg.
Yes. Oh, it was Lüttke who took you! Since we were mentioning Frankfurt, that can bring us back to Karl Friedrich Bonhoeffer.
Oh yes. I feel very sentimentally attached to Bonhoeffer. When I was young, I think it was before my PhD even in Darmstadt, I wrote a paper about the afterglow of nitrogen, and somehow, somewhat attacked the mechanism that Bonhoeffer had suggested, in another paper. And then I met Bonhoeffer at a meeting in Göttingen. I don't know whether that was at the time I was in Göttingen for the year, but it doesn't really matter. Anyway he was there and I met him, and I was enchanted by his personality, and the way he took this criticism! We were friends ever since. He was at that time at the Haber Institute in Berlin-Dahlem, as one of the section heads. But very soon after that he got this "Ruf" to Frankfurt and he established the Physical Chemistry. There was a new building. I don't know whether he built it or what, but at any rate, Frankfurt being very close to Darmstadt, I had a reasonable chance to see Bonhoeffer quite frequently, and I valued his friendship very very much because he was not only a really first rate scientist but he was also a very warm personality and also very very courageous personality. For example, when the Nazis came, he was editor of some collection of books. He wanted me to take on one of these books. That was before I was starting my own books, you see. And so the publisher began to hesitate, sending a contract, because I had some problems with the Nazis. And he wrote a fantastic letter to the publisher about that. He really had courage. And of course, I didn't know that, I only knew him and his very charming wife who was the daughter of the famous pianist Dohnani. At that time I don't think I met the children but they had several small children at that time. He survived the war, as you probably remember. His brother didn't survive. His brother was executed because he knew about the plot to get rid of Hitler. I never met the brother, but according to all the stories that I heard he was a really fine person. He was a theologian.
At the time you were at Darmstadt and you had contact with Frankfurt did you travel to Frankfurt for seminars, lectures?
Sometimes, yes. Sometimes. There was also the spectroscopist, Meissner, in Frankfurt whom I mentioned I think earlier who had the same trouble as I had, but he was a full professor, therefore was apparently not affected. But then eventually he had to leave also. But he only had to leave in 1937. I left in 1935. So I visited him also. But my main connection was really with Bonhoeffer. Not all that frequently, because he was busy, I was busy. He wrote a book on photochemistry, I think one of the first books on photochemistry, and I helped him with some illustrations. He wanted some illustrations of predissociation and things of this sort, and I gave him some help in collecting information about that.
Yes. I still have the book here somewhere. I'm not sure that I can pick it out now. But he was one of my heroes. He came, incidentally, to Ottawa right after the war. I think Steacie had seen him at some occasion and told him he should come to Ottawa, that I would be glad to see him and so on, and he did actually come and he did stay with us. He was just here for two days. You could see how he had suffered during the war. But he was still the fine personality that I knew.
So you have several heroes. One was Bonhoeffer and you also pointed out how much Professor Rau at Darmstadt meant to you.
Oh yes, Professor Rau in Darmstadt, oh yes, he certainly meant much to me, he was not a great scientist, I mean, in the sense that Bonhoeffer was, but he was a great personality. I mean, a very fine personality. And then of course there was James Franck. And the one equally important was Kastler, Alfred Kastler.
Oh yes, you haven't mentioned him.
No, I haven't. Scientifically I didn't have all that much connection with him, although I have a collection of his reprints, but he of course was from the Alsace.
You met him at conferences?
Yes, at conferences of the Joint Committee for Spectroscopy of the International Union. That's where I really first met him, oh yes, I remember that very well. But it was also in connection with the Spectroscopy Commission. He was at the meeting to honor the 100th anniversary of Rydberg in Lund, 1954. That was one reason why I went over. And he proposed a toast at the banquet or something, but he did it in such an elegant way, in just beautiful French. But then I also met him at another meeting. He was in the executive of UPAP when I was also in the executive. We had a very fine meeting in Basel in Switzerland of the executive, with an excursion to one of the Roman relics near Basel, and then we had dinner at some place in the neighbourhood. Kastler was asked to say a few words, and it was just fantastic. He was born not very far from Basel, in the Alsace, in Colmar, and the language with which he grew up was very similar to Swiss German, and so he gave a speech in German mixed with Swiss German and French, it was absolutely delightful. He was not just a person who was humorous; he was also so genuine. Kastler got the Nobel Prize for something that lay at the basis of the development of the laser. But anyway I was very very fond of him. In the 1970s he sent me a book of poems that he had written, and I found out that he had actually at one time intended to be a poet. Then he turned to physics. But the book of poems for me was one of the most remarkable things to get, because it was called "Europe, Ma Patrie: Deutsche Lieder Einer Französischen Europäers." And these poems were really—I still of course have the book with his dedication in it—well, they made you cry. They were written mostly during the occupation by the Nazis, you know. Fantastic.
Do you have this book here or at home?
OK, I would ask you to show it to me, but another day.
I can still bring it along tomorrow if I don't forget it.
That would be very nice.
I think he would certainly have had a chance to become a poet, if he had chosen to do so. And his wife was equally likeable and genuine. I spent quite a few times at their place in Paris. An absolutely remarkable family. In fact, I have a picture of him. If you look back in that corner there.
I will look at it after we're finished. And I think we have almost concluded. Should I give you the chance at the end to pick out either a spectrum or a project which has given you the most scientific satisfaction, or excitement?
Well, I can try. But it really would require some thought. We have for example gone through the quadrupole spectrum of hydrogen, which certainly was in that list, if I call it a list, and of course the spectrum of CH2 has given me a great deal of pleasure, and then the spectra of oxygen and hydrogen. Now, where do I choose? It's very hard to ...
You don't have to.
I think I'd better not even try to. I feel that my scientific life has been rewarding beyond anything that I deserve. So even if right now I feel I am in a period where I don't seem to make any progress in my research. I'm now trying at least to re-establish the three books that I wrote in published form so that they again are available to people if they want to use them. And of course it has given me a great deal of satisfaction that the books have been read so much. Of course, I can't judge how much they are really read, but they have been spread and bought and so there must be something in them that people like. That certainly gives me a great deal of satisfaction, because I'm not a person who writes easily.
Really? That doesn't show.
No. It really took a long long time, I have estimated that per printed page, I spent a full working day, at a time when I was still working hard. I mean, now I can't say if I have a full working day because of interruptions. I'm too old for working hard. But I worked really hard, and if you think of the number of pages that there are, some 2000 pages, 2000 full working days, that's a lot of time of one's life. So to find that a book like the one on the atomic spectra, which was published in 1936, and is therefore 53 years old, is still being bought—in paperback! The number of copies sold in paperback is over 100,000. Over 100,000 now. And Prentice Hall was giving up the book after they had sold 2000 copies or 2500! (Laughter!)
When a call for papers dedicated to the 75th birthday of Rau was issued, it turned out that G. H.'s paper submitted to the Zeitschrift fur Physik was the only contribution.