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Interview of Robert Maurer by Lillian Hoddeson on 1981 March 15, Niels Bohr Library & Archives, American Institute of Physics, College Park, MD USA, www.aip.org/history-programs/niels-bohr-library/oral-histories/4762-2
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Family background. Born 1913; school and university in Rochester, New York. Undergraduate chemistry major; Ph.D. in physics (Lee DuBridge), 1939; Massachusetts Institute of Technology as postdoc (Arthur von Hippel). War work at University of Pennsylvania, silicon diodes; with Frederick Seitz at Carnegie Institute of Technology, 1942-1944, working on Dark Track tube subcontracting, in conjunction with MIT Radiation Laboratory. University of Chicago in 1944 to join Eugene Wigner's group in the Manhattan District; Leo Szilard's graphite calculation and Maurer's experiment; Argonne National Laboratory visit in 1949. Discussions of published works on cuprous iodine, 1941; electrical properties of semiconductors; photoelectric effects, silver chloride and silver bromide. Head of the Office of Naval Research, Physics, 1948. From 1949, at University of Illinois, building solid state physics group.
I believe that last time we got to the end of your short period at Penn, and stopped just at your transition to Carnegie.
After I had been at Penn about only six months, Fred Seitz, who was there, left to become head of the department at Carnegie and I went with him. That was in 1942. At Carnegie, we had a sub-contract with the Radiation Lab of MIT, and did some work upon a highly-specialized form of cathode-ray tube, called the dark-trace tube, which had an alkali-halide screen with a built-in memory.
Was that something new?
It was relatively new. It came out of all of the work that had to be done in the twenties and thirties upon the effects of radiation on alkali-halide crystals.
Are you referring to the work of Pohl and his collaborators?
At Gottingen, I guess.
At Gottingen. And other people to, but Pohl was a principal person. And it had been found that the alkali-halide crystals could be colored, and one method of coloring them was to bombard them with electrons. A potassium chloride crystal became a deep magenta color, so if you evaporated a thin film of potassium chloride onto a glass plate and then bombarded it with 10 keV electrons, which were focused to a small spot, if the spot were then scanned over the potassium chloride screen, it would leave a magenta trace behind, and the magenta trace was more or less permanent. It could be erased by either heating the screen or exposing it to very intense light, and the hope was to produce a cathode-ray tube with such a screen which would retain a memory of the trace that had been put upon it. This was highly desirable for radar purposes, where the fluorescent screens that were used had very short lifetimes; the trace disappeared very quickly. The tube was never terribly successful, because it was just too permanent; it was difficult to erase sufficiently quickly. And of course, eventually with the development of solid-state electronic circuits, you could build a memory into the circuitry and didn’t have to rely upon the screen itself. The original development of the tubes was actually a German thing; they called it the Blaupunkt tube.
Yes, although I don’t believe that the name was really associated with the color of the screen, I think it was a proprietary name, the name of a person or an organization. At any rate, we worked upon these tubes, and at that time, I became acquainted with Otto Stern and Immanuel Estermann, who had been at Carnegie, doing work in molecular physics, but who joined this sub-contract working upon the dark-trace tubes.
So a big operation took off suddenly just about 1942 at Carnegie.
And Carnegie has been important ever since in solid-state physics.
Yes, well perhaps a little background will be of some value. Carnegie had had a good teaching physics department, but had never been very active in research prior to 1942; the Depression had hurt them very severely. One thing that did happen was that during, I believe, the middle thirties, when Otto Stern and Estermann left Germany, as many German physicists did, they came to Carnegie, and they started a really excellent research program.
They were both Jewish refugees?
They were both Jewish refugees. Otto Stern was an extremely distinguished physicist at that time. He had already done his work in Germany, on the Stern-Gerlach effect, which was one of the clinching experiments convincing people that quantum mechanics worked, and with Estermann he had done the Stern-Estermann experiment, where they had shown that you could get diffraction of molecules or atoms off of a crystal surface. Germer and Davisson had done this experiment with electrons, demonstrating the wave nature of the electron, but it was really terribly exciting to see that even a heavy particle, a relatively heavy particle like a helium atom, had a wavelike character. Stern was an extremely profound thinker, and Estermann was the man who did the experiments. Stern could not have screwed a nut on a bolt all by himself. But they began, they continued experiments on molecular beams that they had begun in Germany and with very limited facilities had a very distinguished little group going at Carnegie at the time that Seitz and I came. That work was pretty much stopped, almost entirely stopped, after then, because they became involved in this sub-contract with the MIT people. And at the same time, Oliver Cecil Simpson, who had worked with them on molecular beams, became involved with Emerson Pugh on some ballistic experiments for the Army, involving shaped charges. These were anti-tank, anti-armor weapons. I should say that at the same time that Seitz and I came to Carnegie, Koehler came also, and we worked on these problems from the middle of ‘42 to the end of ‘44, a couple of years. And then, at that time, we were approached by the people from the Manhattan district to join that project, and Seitz and I went to Chicago, and I was in Chicago for about a year and a half.
Right. I’d like some background about that group there as well. You were part of the Met lab, and worked with some affiliation with Cyril Smith, I guess.
No, I was not associated with Cyril Smith on the Manhattan project.
Who were you working with?
Well, I was nominally part of Eugene Wigner’s group, but worked with, and you know, I’ve forgotten his name, a chemist, who came from Notre Dame. And the background here is the following. We were asked to come to Chicago to discuss possible experiments that might be useful. We went and spent one day there.
You said “we”.
Seitz and myself. And we learned the following: that the Hanford piles were about to be put into operation to manufacture plutonium, but there was grave concern over their stability. It had been discovered that under intense neutron irradiation, the carbon atoms in graphite were displaced from their normal lattice sites into interstitial sites and that this disorder of the graphite was a way of storing energy in the graphite. The disordered graphite had more energy than the original, undisturbed, undistorted graphite.
I wonder how this was discovered, and by whom.
They had been doing experiments on the graphite, and I don’t know the people who were involved there. They had discovered, for example, that the dimensions of the piece of graphite changed and the thermal conductivity changed, and these changes were, in view of what one knew about the theory of crystals, undoubtedly due to the displacement under neutron bombardment of carbon atoms from their normal lattice sites into interstitial sites, producing two kinds of defects; vacancies in the normal graphite lattice and interstitial carbon atoms in the spaces between the normal lattice carbon atoms. Now, Szilard had made a calculation, a very rough calculation as to the amount of energy that was stored in the graphite as a function of the radiation dose and had come to the conclusion that it might be very dangerous. There were a number of concerns, but this was the primary one. The fear was that if a local hot spot developed in a nuclear reactor, perhaps as a result of some imperfection in the cooling arrangements at a given point, that the graphite would heat up and, as it heated up, it would anneal, that is, the damage which had been induced in it would be removed. The abnormal atoms would migrate back to their normal lattice sites, and this would release the energy that they had had in their abnormal sites. This release of energy would further heat up the graphite, and you might have a really explosive release of energy spreading throughout the pile. There were even jokes at that time that instead of making a bomb, one should make a reactor and drop the reactor on the Germans.
So Szilard played an important role in …
Szilard was an absolutely key person. There were other things that he did that were more important, but he made this little calculation, and he made everybody intensely worried, because they were starting up the Hanford piles, and they had no knowledge at all, no experimental data on what the amount of stored energy was. Szilard was very quick to say that his calculation was a worst case.
Was he at Chicago at that time?
He was in Chicago. What Szilard couldn’t do was calculate how much annealing might go on, even during the irradiation itself. The neutrons were not only displacing atoms, but they might also cause some of them to go back to their normal lattice sites. So his calculation was a worst case, but it looked bad enough that it worried people. Well, we were asked whether we could do anything about that, and Seitz and I discussed it, and concluded that it would be possible to do a very quick experiment that would at least give the order of magnitude of the energy. I should say that a group of physical chemists had been working at Chicago for I think almost a year building an apparatus to do this job and so far hadn’t succeeded in making it work. The next day I took the train back to Pittsburgh, and collected a graduate student and some equipment and the next night we took the train back to Chicago. We were given a deadline of seventeen days, and …
This was some time in ‘44?
This was in about ‘44. I don’t know exactly, I’d have to check. I think I still have some data, some records, but it was late in ‘44, or early in ‘45.
Sometime when you’re in the mood to look for those …
I’ll try to find them.
... that would be very useful to us.
The graduate student, Mr. Ruder, and I set up our apparatus. It was very crude and all of it was on top of one table, and just before the seventeen days were up, we had the data, which was very reassuring. We only measured that part of the energy that would come out below 500°C, but that was the critical region of temperature, and the amount of stored energy was not serious enough to be a real danger. At a later date, using a quite different technique, some people at the Bureau of Standards measured the complete energy, actually, by burning the graphite which had been irradiated and measuring the total heat evolved. They found an additional component of damage which didn’t anneal out except at very high temperatures of the order of 1000 degrees. That particular job that was all done in the first 17 days that I was in Chicago was the only really important thing I did during the year and a half I was there. I spent a considerable amount of time investigating the motion of bubbles in fluids, because we were interested in so-called homogeneous reactors, in which the neutron irradiation in a fluid water solution of the uranium salts produced gases hydrogen and oxygen, and we had to be sure that the reactor would be stable in order to know what the bubble content of the water would do to the density and to the fluctuations in density of the water. And I had a lot of fun studying bubbles, but I don’t know that it was ever of any great importance. We did a few experiments upon irradiation damage of graphite; the only significant, thing, I think, was that I think we for the first time observed a change in sign of the Hall Effect. It happened in graphite as a result of neutron irradiation. And I worked on a few things like electromagnetic pumps for pumping metals without the use of valves or seals.
Was this connected with the war effort too?
Yes, this was all part of the radiation damage effort. The electromagnetic pump had been invented by Szilard; it had been used to a small extent for handling metals like liquid mercury in a totally enclosed glass system, but our interest was in reactors, high-temperature reactors, which would be cooled by a molten metal like sodium or a sodium-potassium alloy, and since it was necessary to keep any trace of air or oxygen away from these molten metals, they combined chemically with oxygen releasing a lot of energy. It would be necessary to pump the molten metal through the reactor with a pumping system that was totally enclosed and I did some work; I don’t think we ever really got very far with it. I worked for a while, for a few months, up at Argonne.
I haven’t yet learned terribly much about the origins of the neutron diffraction technique; I gather that came directly out of the war effort. Or is that not so?
No, the origins of neutron diffraction go back to the experiments of Davisson and Germer at Bell Labs.
Electrons. And then, as I mentioned earlier Stern and Estermann had diffracted helium atoms off a lithium fluoride crystal. Well, when you have a lot of neutrons, the obvious thing to try to do is to see whether you can diffract neutrons off a crystal. If quantum mechanics is correct, any particle has a characteristic wavelength, and you can produce diffraction effects. I don’t know who first did the diffraction experiments with neutrons, but by the time I was involved at Argonne, there was a crystal spectrometer set up at the graphite pile, and a beam of neutrons was being diffracted off a large crystal. The intensity of the diffracted beam was very, very small, and one of the very amusing little incidents concerned a visit of Seitz to the group doing this work. They were puzzled by the low intensity of the diffracted beam, which they thought should be much more intense. And Seitz looked at their crystal, which had a very smooth, polished face, and asked for a piece of sandpaper and he rubbed it over the surface of the crystal, practically inducing terminal shock in all of the experimenters. Immediately, the intensity of the beam went up by an order of magnitude. They just hadn’t realized that they really didn’t want a too-perfect a crystal.
That’s great. How long were you at Argonne?
About two months, I would guess.
This was in ‘45?
This was towards the end of ‘45. The work of the Manhattan District was shutting down, and the people at Chicago were already disappearing, and yet there were a few things to be done and I had not spent any time at Argonne, so I went out to Argonne for a few months. It was during the summer, I remember now, it was during the summer of ‘45, probably. I lived out there and worked around the pile. Walter Zinn was in charge of affairs then, and the real effort at that time was to develop Argonne for the future as a nuclear energy site. That’s probably pretty much the story of Chicago. I went back to Carnegie from there.
Let’s see, sometime in this period, you prepared an article, a review paper, on the electrical properties of semiconductors for the Journal of Applied Physics [“The Electrical Properties of Semi-Conductors”, Robert J. Maurer, Journal of Applied Physics, 16, (1945), pp.563-570].
I don’t think there anything special to say about it. It’s a fairly routine effort and I don’t see that it has any special virtues.
It was based on a paper delivered at a symposium at the Detroit meeting, April, 1943.
My memory is that at that time Seitz and I were invited to give a pair of papers and he gave one on the general problem of the electronic structure and I gave this one on the electrical properties of semiconductors.
I noticed that in your paper you discuss Wilson’s holes. I was curious about how widespread this notion was by 1945.
You mean the concept of a hole?
Holes in semiconductors; the concept of a hole I would have thought was fairly well known by then, but maybe not.
I think so. One moment let me just check something. He pulls out a book. Here is Shockley’s book, Electrons and Holes. Now this came out about 1950, so by 1945, the concept of a hole was really well established. Another little anecdote: sometime around 1947-48, I gave a public lecture in Pittsburgh on electrons and holes in crystals. It was really on defects in crystals; I included the topic of vacancies, a vacancy being a place in a crystal lattice where an atom is missing, and a hole is a place where an electron is missing.
This was reviewed in one of the Pittsburgh newspapers under the title “Carnegie physicist discusses trapping of holes by vacancies” — which is one of the reasons why sometimes Congressmen think that people who do research are not quite all there.
I notice that you refer to Seitz’ review of 1945 [J. App. Phys., 16, 553 (1945)], on imperfections in your standard footnotes, and I was wondering whether it was considered the standard reference on that at the time.
Which reference is that?
Journal of Applied Physics; I believe that was an article on imperfections.
Seitz wrote a review article for I believe the Reviews of Modern Physics on imperfections in alkali halide crystals, and that was the Bible.
That was the Bible for everybody who worked with ionic crystals for years and years. It. was one of those few review articles that really had a profound impact upon the whole area of research. It was terribly important.
That’s the sort of thing we want to recover, information about which articles really had an impact.
What Seitz did was summarize all of the work that had been done at Gottingen during the thirties by Pohl and his co-workers, Hilsch and Pick, and tie the experiments together with theory. One should understand that the German group at Göttingen was superb experimentalists, but their theoretical interpretation of their results was fairly elementary. Seitz put it within the framework of a modern, theoretical approach, and just showed people that there were scores of interesting things that weren’t understood, which were both scientifically interesting and potentially valuable if you could understand them. No, that review article of Seitz was one of the great review articles in solid-state physics.
Well, let’s see, now you’re back at Carnegie and the first, or one of the first articles is a report on some experiments on optical absorption bands in alkali halide crystals. [“Optical Absorption Bands in Alkali Halide Crystals,” C.C. Klick and R.J. Maurer, Physical Review Letters, 72, p. 165, (1947)] It’s about a monochromatic for studying F and M bands.
It was one of those papers which a graduate student gives because he really wants to show that he’s making progress towards his thesis.
I went back to Carnegie at the end of ‘45, beginning of ‘46, sometime there and immediately started a research effort which had two aspects, one was to study the mobility of ions in alkali halide crystals, and the second aspect was to study the interaction of electrons and holes with vacancies in alkali halide crystals. Between ‘46 and ‘49, a period of about three and a half years, I had five graduate students who got their Ph.D.’s,
That was a very intense period. I taught three courses every semester, and they were different courses every semester, completely revamped the modern physics laboratory, building a lot of the apparatus myself, we remodeled the physics building and. some of the advanced courses right after the war. You couldn’t get American texts. I taught a course in electrodynamics one year of Becker’s Theorie der Elektrizitat, and the graduate students had to learn German.
Is there anything special to say about your Encyclopedia Britannica article on photo electricity [“Photo electricity’, R.J. Mr., Encyclopedia Britannica, pp. 787-793, (1947)]?
No. I actually wrote that while I was still in Chicago, and it, oh, it’s all right, but under the pressure of the time, I didn’t give as much space and time to the modern solid-state volume photo effects, photovoltaic effects, etc., as would have been appropriate.
Tell me, did the concept of the work function originate with Einstein’s paper on the photoelectric effect or was the concept around earlier? This is something I have not yet probed.
I would suspect that it came earlier. If one looked in the Hughes and DuBridges book on photoelectric phenomena, one might be able to pick it up. Hertz discovered the photoemission of electrons, and it was fairly early discovered, I think, very soon after the original observation that you had to have light of a certain wavelength, shorter than a certain wavelength, which depended upon the metal, in order to get emission. Typical metals like zinc that were used wouldn’t emit in the visible. I think the notion of the work function antedated Einstein and what I don’t remember at all is whether it first came out of the photoelectric effect or out of thermionic emission, because the emission of electrons from a heated metal goes back to Edison. People like Dushman and Richardson developed a theoretical equation for it, and the data is analyzed in terms of the work to extract an electron from the surface of the metal, which is the work function. So it’s possible that the concept of the work function actually originated in studies of thermionic emission. I don’t know anything about that early history in fact; the photoelectric effect may have antedated the thermionic emission studies, and probably did, because it goes back to the early part of the early decade of this century.
I haven’t had a chance yet to look into that early background, though I will of course have to, and want to.
Well, there’s plenty of data available, I simply don’t remember what came first.
Two papers that I will need to go back and read are the early papers of Drude and Lorentz, in which they calculate many of these phenomena on the basis of the free electron theory. I’m pretty sure they calculate thermionic emission, but I don’t know whether they consider photoelectric phenomena.
There used to be review articles, you know, which contained it all rather well. Actually, one of the books that have a good deal of this in it is the book I used as a text in that course at Carnegie, Theorie der Elektrizitat, by Becker. This came out in 1933, and he has the Elektronentheorie der Metalle, which starts with the Drude theory, page 195, there might even be a reference.
Drude is 1900, isn’t he, in Annalen der Physik, Lorentz is, relatively for that period, soon after, within five years.
That period at Carnegie just after the war was a very fruitful period in which we began some interesting things on F-centers in alkali halides. But the important things that we did were the studies of self-diffusion of ions in alkali halides; I had a series of students who worked on this. Yes, Dillon Mapother was the first of them, and there was Howard Etzel, and a man named Crooks. Those were among the first papers using radioactive tracers; this paper here of Etzel’s was for 10-15 years one of the most cited papers in the field. It’s a very simple thesis, but the results are exceedingly straightforward, and they demonstrate the effectiveness of the theory exceedingly well [“The Concentration and Mobility of Vacancies in Sodium Chloride,” Howard W. Etzel and Robert J. Maurer, The Journal of Chemical Physics, 18, 8, pp.1003-1007, (1950)]. This paper of Crooks and Mapother was one of the first of the important studies of self-diffusion of sodium ions [“Self-Diffusion of Sodium in Sodium chloride and Sodium Bromide,” Dillon Mapother, H. Nelson Crooks, and Robert Maurer, The Journal of Chemical Physics, 18, 9, pp.1231-1236, (1950)]. When I came here, we continued that work, and refined it a good deal.
How did these studies of the self-diffusion begin?
Well, the work began because through my contacts at the Met Lab, I had realized that, with reactors going after the war, there were going to be radioisotopes relatively available, in a way that they had never been before the war.
So this work was a direct consequence of the war.
It was a direct consequence of the fact that reactors had been built, and were working at Oak Ridge and at Argonne, and that you could take a sample of sodium chloride and ship it to Oak Ridge, and they would irradiate it in the nuclear reactor, and a week later, you’d get it back, and it would contain radioactive sodium, And now that radioactive sodium could be used as a tracer, what you do is the following: you take a crystal of sodium chloride, and you evaporate some of this radioactive sodium chloride on the surface. And then, if you heat the whole thing up, the radioactive ions diffuse in, and then you slice up the crystal, and you measure the amount of activity in each slice.
— which is proportional to the number of ions that have diffused in that distance. And you get a curve of radioactive sodium as a function of distance, and from the shape of that curve, you can calculate the diffusion coefficient of the radioactive sodium. In principle, exceedingly simple, technically rather difficult. We had to slice up a crystal into slices which were about 10 microns thick, and to do that, Mapother had to develop a very special microtome. The whole technique was carried to the utmost by people like Dave Lazarus, dealing with metals, and a man of that …
In the same period?
No, later. But, I think we were reasonably early here, amongst the first to do this sort of thing. There had been some studies, principally on metals using naturally radioactive materials, as early as 1915, but there just wasn’t a lot you could do, because you didn’t have the right isotopes available. We got in fast and quick with these measurements.
One of the things that struck me about these papers was their interdisciplinary quality. I mean it was a combination of physics, metallurgy, technology and chemistry.
Well, all of this work involves some chemistry because typically you’re working, not with a pure sodium chloride crystal, but one that contains a little added cadmium, or calcium, or strontium, and you have to measure the amount of the added additive, the strontium or the calcium, which is typically of the order of one part per thousand. And that’s a fairly tricky thing to do if you want to do it within, let’s say, a few percent. You want your numbers to be precise within a few percent. And so, we used polarographic techniques at times; here, one of my students developed a nephelometric technique, a light-scattering technique for working with calcium, but there’s a fair amount of chemistry involved.
Well you came out of chemistry, in a way.
I was an undergraduate in chemistry.
What about your students?
Mapother was a mechanical engineer; the others were almost entirely from physics. I don’t think there’s much more to say about the period at Carnegie.
I have one question about your, interest in optical properties. Was there any connection, do you think, to your early background in Rochester, where you certainly were in interaction with people who cared a lot about photography?
If there was a real effect, it was subconscious.
Before I came here, there was one period it might be worth saying something about. In 1948, I took a leave of absence from Carnegie and went to Washington. For about a year, I was the head of the physics branch of the Office of Naval Research.
What did you do there, and how did that happen?
Well it happened because, again, Seitz and I had maintained contacts with people in Washington, and was very much aware of the fact that the Navy, which had established what they called the Office of Research and Inventions during the war, was interested in carrying on some form of interaction with research people after the war. And when they began to offer support, we were amongst the first to bid for it. And it was in talking with these people, that they became aware of you, and you became aware of them. The Navy had already established what they now called the Office of Naval Research. One day, one of the men called me up and asked me whether I’d be interested in coming down and working with them. It was a rather exciting possibility because the whole outfit was completely new, and I took a leave of - absence and went down there. That was a very exciting period, and I felt a very fruitful period. In the history of postwar solid-state physics, in fact, all physics, the Office of Naval Research is a very important factor. The Navy had been terribly impressed with what science and technology was able to do for them during the war. You see, radar made orders of magnitude difference in their fighting capabilities. There was one admiral who came back from the Pacific during the war just glowing, you know his radar would tell him that the enemy was on the way, and he’d have his guns all lined up before they knew he was there. The only thing he objected to was, he said, “get those damned antennas off the top of the ship, where they get shot away, put them down inside the ship.” He didn’t realize, if they were inside the ship, they were useless. But it was not just the homing torpedoes, a whole tremendous amount of technology. The Navy was just terribly impressed, and immediately after the war, the Navy had money, because their appropriations didn’t disappear as fast as their expenditures for operations. They set up this Office of Naval Research. The prime person, I believe, was a Captain Conrad, and really somebody ought to do some research upon his background. He died relatively soon after ONR was established, of cancer. One of the people who had worked with him, and who was still around when I went there, was a man named Dr. Urner Liddel. And Liddel was an exceedingly important figure in it. You see, it wasn’t just establishing a concept, but it was the setting up of the framework, the organizational structure, which was superb. And they got some excellent Navy people who headed it up; when I was there, Admiral Lee was the commander-in-chief of ONR, and he was just superb. But they were lucky in that they had a group of very unusual people. In my group, the physics branch, I think we had five people. There was Lawson McKenzie, Bert Annis, Frank Isaakson, Elizabeth Kelly, and myself. And you know there were five people for a budget of about 2 million dollars a year. Today, in the National Science Foundation, that number of people would probably handle ten times the amount of money. We knew every one of our contractors personally. We visited them at least once or twice a year; the people were technically rather competent, very very interested, very hard-working. There were certain principles that were terribly important. One was that we didn’t solicit proposals. In the fifties, the Army set up the Office of Army Research, the Army Research Office, and the Air Force established the Office of Scientific Research of the Air Force. And out of this, and principally out of ONR, came the National Science Foundation. There were a great many people who looked with some skepticism upon the idea that the military were supporting basic research in the universities, and they felt there ought to be a civilian agency to do this. Some of my friends didn’t like the idea that one went to Washington to work with the military. I thought they were crazy, but that was another matter. The original science foundation owed its concept and even its method of operation to the Office of Naval Research. So, the Office of Naval Research was one of those critical organizations. It did certain things which were eventually of tremendous value. It started the whole low-temperature set of projects across the country. A man at MIT had invented a small helium liquefier which cost about $15,000, which was a lot of money. The Office of Naval Research made these available gave these liquefiers to selected people around the country. And that was how low-temperature research got its start in this country.
This is Collins?
The Collins machine, invented by Sam Collins. And Arthur D. Little began to manufacture them. Eventually, they spread all over the world.
You know, I don’t know the background of the Collins liquefier — where and how it was discovered, and why, and whether the discovery had to do with the war. I just know that it had a tremendous impact on solid- state research.
Well, the basic principle is very old. I don’t really know what it had to do with the war either, although I think it came out of the fact that during the war, there was a great need for liquid air, and liquid nitrogen, and liquid oxygen. And so people began to look at more effective and simpler ways of making these liquefied gases. The basic idea is to do what is called adiabatic work, which cools the gas until you get it to a temperature low enough where an irreversible expansion through a nozzle will actually make it liquid. That’s the Joule-Thompson effect, and it’s very, very old. But the problem with a liquid helium machine of this sort is that you have to have a machine that does work; typically, you have to have pistons that go up and down and which are driven by the gas, by the compressed gas. But pistons have to be lubricated, and when you get down to liquid nitrogen temperature, there aren’t any liquids that you can use to lubricate. You have to use the helium gas itself to lubricate your pistons. And this was what Collins was able to do. He provided a small, compact, easily-operated machine. But it was expensive, and Lawson McKenzie got the idea that ONR could make a contribution to basic research by selecting maybe half a dozen places around the country which were capable of using these machines, and then giving them to them, and this was done.
I wonder if this history has been written at all.
Some of it, yes. The Navy has put out a kind of a history of the Office of Naval Research. It would be well worth looking at.
I’m wondering how to track that down.
Write to the present Office of Naval Research and ask them.
That’s a good idea. This is certainly something that we should be aware of and make use of.
Well, there was just a tremendous amount of first-class work supported. It was easy, because there were lots of good people just coming back from war work, who wanted to start basic research. They needed equipment; they needed money to support graduate students. And furthermore, we had money. Two million dollars even then wasn’t a lot, but it was in fair harmony with the demand, and each year you could go over to the Bureau of Ordinance, the Bureau of Ships, at the end of the fiscal year and pick up two or three hundred thousand dollars which they couldn’t spend, and which they’d transfer to the Office of Naval Research, so in the spring we always had a great rush of proposals.
I didn’t realize that there was a significant amount of money left over from the war which was then fed into science in this area.
You see, these bureaus still had big budgets, but their operations had contracted, and the last thing any Washington agency wants to do is give money back. So, you spend.
Who figured out that this was the place to get money for research, and got them to take this direction?
You mean to give it to the Office of Naval Research.
And to have the Office of Naval Research spend it on research.
Well, it was Captain Conrad, or Urner Lidell, who sold the idea to the top brass of the Navy that it would be in the Navy’s interests. The Navy had a group of good laboratories, Naval Research Laboratory, the Naval Ordnance Lab; they had just built the Michelson laboratory out in California. There was the Naval Ordnance Test Station at San Diego, and they built the Navy Radiological Laboratory in San Francisco. The Navy was a really technically-minded organization, very different from the Army or the Air Force. In the Air Force, most of the people were civilians who had come in from all walks of life. The Air Force bought its planes from the plane manufacturers. The Army typically had an engineering core, but it was primarily concerned with things like moving earth, and building buildings. But the Navy had a long tradition of ordnance, technology of ordnance, of gun sighting, range finding, weather prediction. The Navy was relatively sophisticated all through the thirties in its level of technology and its interest in technology, and it saw the virtues of basic research. Very few people know it, but Alfred Michelson was a graduate of Annapolis, and he made his reputation measuring the velocity of light. He left the Navy in order to spend full time on his research. But when the Navy built the Michelson laboratory in California in the Mojave Desert, I was there at the dedication and Robert Millikan gave the dedicatory address. He began by saying that it is undoubtedly true that the most distinguished graduate that Annapolis ever had was Michelson. There were at least 50 admirals there who showed that they didn’t believe a word of that. But the Office of Naval Research was one of the great institutions and made the transfer from wartime research to the basic research at the universities possible. There were some queer characters. We, I say, knew all the people, all the contractors personally. One of the people we had was Jesse DuMond, a very fine physicist. He was doing X-ray crystallography and gamma-ray crystallography. He had a small contract with us, and one day called up and said, “After we got started, we realized there was a much better way of doing what we were doing, but it would be much more expensive.” And he said, “We had to make a decision. As a result, I’m broke. You’re going to have send me some more money.” And I said, “Look, we’re out of money. We don’t have more money. How’d you get into this terrible position?” And he told me the story of how they realized they could build a much better instrument than they had originally planned, but it would be much more expensive. He said, “We had to make a decision, and we decided to spend courageously.” Well, that became a byword in ONR; whenever we had one of our contractors whom we couldn’t hold within reasonable amounts of expenditure, why we referred to them as someone who spent “courageously.” But, perhaps the best thing I ever did at ONR was, in order to get out of the job once I was in there, in order to get back to Carnegie, I found that it was necessary for me to recruit my successor. And my successor, whom I recruited from the University of Pittsburgh, was Elliot Montroll. Do you know Montroll?
One of the very fine people who had a great deal to do with the success of ONR was Manny Piore, who was the deputy commander, the civilian deputy commander. Manny Piore went on to IBM. He’s retired now. Well, I went back to Carnegie at the end of ‘48, and then at the end of ‘49, of course, I came out here with Seitz, and brought Dillon Mapother with us. We’re getting now to the period of the fifties.
Yes, and we’re about to talk about your transition to the University of Illinois, which I think is worth explaining. Just one more question, was Benjamin Vine another graduate student at Carnegie?
You did a joint paper with him on cuprous iodide, which was an earlier interest of yours, in about 1951 [Benjamin H. Vine and Robert J. Maurer, “The electrical properties of cuprous Iodide,” Zeitschrift für Physik, 198 (1951), pp. 147-156].
Yes, that’s right. Vine was a graduate student who wanted to do a semiconductor thesis because he wanted to go into industrial research. And I harped back to what I thought was an unfinished bit of work, the earlier work on cuprous iodide. With the facilities we had available at Carnegie, one could do a Hall Effect, and if you’re studying the electrical properties of a semiconductor, at a very minimum you want to measure the electrical conductivity, and you want to measure the Hall Effect. The two things give you the number of charge carriers and the mobility. And unless you make both measurements, you’re very limited in what you can learn. So we did the work on cuprous iodide. It was a very nice piece of work on Vine’s part. Cuprous iodide turns out to be complicated, and I don’t feel that the results contributed that much to the development of semiconductor theory, simply because we picked too complicated a material to work out. Really important things were being done with the very simple semiconductors like silicon and germanium. That almost ended my interest in semiconductors; I transferred all my attention to the alkali halides.
The transition to the University of Illinois took place about 1949.
What happened was that Seitz was the head of the department at Carnegie. He had more or less decided that the opportunities for developing the department at Carnegie had reached their limit. After the war, he had brought in Ed Creutz, who was one of the critical people in the Manhattan district, and had been very closely associated with the construction and the development of the bombs at Los Alamos. With Creutz and the cooperation of the electrical engineering department at Carnegie, the Carnegie synchro-cyclotron was built, and that was one of the half a dozen very large, for that time, synchro-cyclotrons, and probably the best-designed one. The group at Carnegie under Creutz just did a masterful job of designing it, and it was a beautiful instrument. But when that was done, it was clear that the Industrial people around the Pittsburgh area didn’t have the concept for example of developing Carnegie into a competitor of MIT. The future looked as though it was not grim but limited. I think at the same time Seitz wanted to get back full time to research and get rid of the chores of being a department head. And, of course, he had known Loomis very well from the days of the Radiation Lab at MIT.
Oh, I didn’t realize that that was where they’d met.
And then there was the man who came here from the Radiation Lab and who had been at Pennsylvania, he came as dean of graduate studies here.
Ridenour was very well known to Fred, and so Fred Loomis and Ridenour talked together and Fred decided to take a professorship here, and then he persuaded Jimmy Koehler and I to come with him. And the idea was to start a solid-state group here. Loomis and Ridenour felt that a postwar physics department that was going to be of national importance had to have, in addition to nuclear physics, had to have a strong solid-state physics group. So, we came out and we started the group. Mapother played a critical role because we wanted a low-temperature research area, and he took on the responsibility for developing that. He installed our Collins liquefier, and collected some graduate students and began research in low temperature. Eventually, of course, people like John Wheatley came, but the period from ‘49 to ‘55 was another one of those very busy, very fruitful ones, in which all of us got out a lot of good research, under rather difficult positions, we were living in the attic of the old physics building, with rather poor facilities.
Why do you put a cut-off at around ‘55? Did something change then?
Well, I’m thinking of myself. Things began to change around that time for myself. One thing that happened at that time was the Korean War, and the Korean War had a number of effects. For example, in Washington, the Office of Naval Research was changed, and never really was the same again, because, as a result of the Korean War, the Navy began to put more and more emphasis on applied research, and began to insist that the basic research that was supported by the Navy be relevant. That’s the death of basic research, when you demand that it be relevant to something. Here, the Korean War resulted in the establishment of what’s now CSL, the Coordinated Science Laboratory, and Seitz was instrumental in setting that up. The first thing they did was they took over the space, the new space that had been created for the solid-state physics community.
This is just about ‘55?
‘57. But it was also true that Seitz began to spend more and more time in Washington, around the country, the size of the solid-state physics group got larger and larger, we had more and more contracts. I found myself spending more and more time just doing what was sort of unofficial administrative work.
So there was a real change in the quality of the research.
Oh no, the research as a whole here got better and better.
Perhaps the change was rather in the way in which the research was done, in the environment.
Oh, the environment got better and better. There may be confusion here. On the one hand, I’m referring to the totality of what went on here. Things like Bardeen coming; that was enormous. And Nick Holonyak coming, and Dave Pines. Things got better and better here, but my role was another matter. I had always been closely associated with Seitz, and as he spent more and more time away from the place, I spent more and more time doing things that otherwise he would have done here. He took a leave of absence to act as science advisor to NATO, it was about ’59-‘60; he spent several years in Paris. And that was a period when the Advanced Research Projects Agency was established in the Pentagon. Well, I must back up a little bit. Back in the very late fifties, around ‘58, ‘59, Seitz had been talking with the people in the Atomic Energy Commission about the limitations upon the ability of the universities to do basic research. He felt that the bottleneck had become space. For instance, here we could get the money to do the work that we wanted to do, but we didn’t have the facilities, the rooms, the gas, the electricity, and so on. New space was necessary. John von Neumann, of the AEC, was very sympathetic to this point of view, and the AEC indicated that it would probably make some buildings. We put in a proposal for a new research laboratory to be built by the AEC, and it was necessary at that time to get authorization from Congress. Congress passed the authorization bill. We felt that we were in business. The money got knocked out of the appropriations bill, largely, apparently, because of rivalry and feuding between various congressmen. Melvin Price was the man who was spearheading our effort and his friends from Michigan and Missouri knifed him. I never knew quite why, but we lost that. That was in 1960, and at that time, Seitz was abroad. In all of this I had been doing a great deal of house work here. Well, the Advanced Research Projects Agency had indicated that they were interested in making funds available for interdisciplinary laboratories, and as soon as it was clear that we couldn’t get building money from the AEC, why we went to ARPA with the proposal. Now, ARPA made its first grants in ‘61, and we were passed over at that time. MIT, Penn, and Cornell, I think, were the three that were first authorized. But in 1962, a proposal of ours was accepted by ARPA, and our proposal was unusual. You see, we had very close ties with the Agency because, in particular, of people like Koehler, who were doing radiation damage work here that the AEC was very much interested in. And the AEC didn’t really want — they really wanted to go ahead with some form of relatively massive support here, but they couldn’t build a building. So our proposal was for joint funding of a new laboratory, the Materials Research Laboratory, with roughly half of the funds coming from ARPA and the other half from AEC. The proposal was that the AEC, which was funding about three-quarters of a million dollars of basic research here in physics and metallurgy and chemical engineering, they would double that to about 1.5 million, which would be obtained over a five-year period. The first year, ARPA put in 50 thousand, and then year by year, until at the end of five years, it would reach 1.5 million. And the ARPA was going to build the building. The AEC put in 20% of the building funds. The building cost about 3 million dollars. And that was the beginning of the Materials Research Laboratory. Late in ‘61 we knew we were going to get it. And Seitz had returned from Paris, but he was now becoming dean of graduate studies here, and somebody had to take over the direction of this new laboratory. In particular, we had to build a building. And so, by ‘62, I was essentially out of research, because I took over the directorship of the new NRL laboratory, and for two years, ran the laboratory, using space in various buildings, metallurgy, physics, and chemistry. And I knew we had to have facilities, very specialized facilities. So I began to buy instruments and to acquire some personnel. For about two years, I operated a mass spectrograph which was a big instrument for us in those days, it cost $150,000. I ran it in the basement of this physics building. And then, in ‘64, we began the construction of the NRL building, and finished it in ‘66, and moved in ‘66. George Russell was the associate head of the laboratory in those years and also associate head of the physics department. He eventually became Dean of Graduate Studies, and he’s now the Chancellor of the Kansas City branch of the University of Missouri. But while I was the director of the laboratory, I found that it was quite impossible for a person of my limited abilities to carry on research at the same time. And I did want to continue teaching, so I phased out of research.
Well, MRL is certainly an important institution.
It was terribly important.
— for this department, and for the subsequent history of solid-state physics. And I think you made a good decision, certainly for other people. It worked out very well.
Well, there are opportunities that arise in the course of events and you either grasp them or you don’t grasp them. This was one that we grasped. For instance, one that was not grasped here, immediately after World War II, there were projects going, well, they began during the war, but MIT, for example, got Lincoln Laboratory right after the war. And Cal Tech got the Jet Propulsion Laboratory. Several other universities got large associated laboratories, some of which in the course of events failed. But, you know, the Jet Propulsion Lab and the Lincoln Lab were two of the successes.
The Radiation Laboratory at MIT. Quite a few of the people around here had been associated with major projects, but this university never grasped any of those opportunities. Chicago, for example, did.
They got Argonne.
Well, they got Argonne, but more than that, they built on the fact that the Metallurgical Lab had been there during the war, and they got a whole series of laboratories supported by the Federal Government immediately after the war. That was an opportunity missed here. In '61-'62, we didn’t miss the boat. And, by that time, it was very important; if you were going to be a major solid-state, metallurgical, ceramic, in other words, materials laboratory. It was utterly necessary that you had these interdisciplinary facilities available, and the only way you could at that time was through these laboratories. If you were to join the MITs and the Cornell’s and the Berkeley’s, you had to have these laboratories.
You produced a few more papers before this switch in your career some of them have not yet been mentioned. For example, the work on the V1 centers in potassium chloride with Dutton and Heller [David Dutton, William Heller, and Robert Maurer “Thermal Destruction of V1 Centers in Potassium Chloride,” Physical Review, 84 (1951), p.363]. Is this something that is worth spending a minute or two on? And there’s more on it [Kenneth Teegarden and Robert Maurer, “V1 and H centers in KCI,” Zeitschrift für Physik, 138 (1954), pp. 284-289].
These papers of Dutton and Teegarden were quite important papers at the time that they were produced, because they almost initiated a technique, a thermo luminescent technique for studying trapped electrons in holes. The interpretation that we gave in these papers to much of the work did not stand up. We thought we were observing the release of trapped holes.
This is based on Seitz’ theory?
It turned out that we were observing release of trapped electrons and the recombination with holes, and this was demonstrated largely through some superb work done at Argonne by a group similar to ours up at Argonne.
Who were the main people there?
The main people up there were Peter Delbecq and Peter Yuster. Yuster and Delbecq were was an excellent team. They were able to show that we were really observing the recombination of electrons and holes, but the holes were still trapped, the electrons were what we’re being freed. One of the very nice things that came out of this was here at Illinois. One of my post-docs was a Swiss named Werner Känzig, and you probably don’t have the paper, because the work was published after he left here, and my name never went on it. For a good reason, because he did it all pretty much himself, but when Känzig came here, he wanted to do some spin resonance work, and I had never done work in that field, but I got the research board at the University to give me money for a magnet, and by the way, that’s one of the great things about this university, the ability to go to a central unit like the research board that has funds and with little fuss quickly get funds. We could not otherwise have done the work of Känzig. The research board gave me $15,000 we bought a twelve-inch Varian magnet. Känzig had spent a couple of years studying the spin resonance of the trapped holes in these crystals. He left here to go to GE, and when he left here, he had just finished taking his data, and it hadn’t been completely analyzed yet.
Late fifties, ‘57. (Maurer rummages through things to find data.) It was ‘57. It came out as a GE report. After he went to GE, he wrote it up and the interpretation that we had expected to give to it on the basis of Seitz’ theory didn’t work. And so, he had to find out what it really was that was producing the spin resonance. Well, at just the same time, this group up at Argonne, Delbecq and. Yuster had also been doing these experiments, and the Delbecq-Yuster group published their results just about the same time. And with the usual result, we people called the center that was responsible for the data the Vk center, and the people up at Argonne called it the chlorine molecular ion, and so in the literature, both of these got carried along, meaning the same thing.
May I just make a copy of this for our working file?
Sure. That work of Delbecq and Yuster and Känzig was just some of the work, it opened up the whole field of hole centers. It demonstrated that hole centers were very, very different from anything anybody had suspected before. What baffled all of us was this: in an alkali halide crystal, where you have a (makes diagram on board) chlorine ion, it would be surrounded by positive ions like this. Now, if this is missing, you can trap an electron in here that has a negative charge, and that’s the so-called F center, which has played a tremendous role in developing our understanding of trapped electrons in crystals. Well, we were looking for the analogue of it, that is, if you have a place where a positive ion is missing, that could trap a hole. [diagram available on paper transcript]
The signal that you see here, the spin resonance, you could predict what it would be like, what sort of wiggles it would have. Well, the wiggles that Känzig got were nothing like what you’d get from this center here. And therefore, this center just doesn’t exist.
Let me just tell the tape recorder the configuration that doesn’t exist is the hole surrounded by, well, in this particular diagram, four negative chlorine ions, and the one that does exist is the electron surrounded by four positive ions.
What happens is that the hole is very remarkable. The hole sits down on two chlorine ions, and of course, you can think of it as a chlorine ion which has trapped a hole, so one of them is neutral. Or, so you can think of it as C12, a chlorine molecular ion, and the hole is shared between these two ions the way an electron is shared in the hydrogen molecular ion. One electron shared between two protons gives you a hydrogen molecular ion; one hole shared by two chlorines gives you a chlorine molecular ion. We had never suspected that such a configuration could exist in a crystal. Then Känzig discovered next that at very low temperatures, the hole could spread out and that was the so-called H center, and a whole new area of study and understanding of the trapping of holes in ionic crystals was opened up as a result of this work, and of course, others. The Yuster-Delbecq group at Argonne was at that time, I think, the finest group working in the field. Fritz Luty and Heinz Pick at, uh...
Not at Gottingen. Stuttgart. You know, I’m getting old, my memory is shot. Well, anyways, Fritz Luty and Heinz Pick. Heinz Pick’s models of these centers were the ones that eventually turned out to be correct. He invented many of the models which proved to be correct whereas others by people like Seitz didn’t hold up.
I noticed in the paper with Dutton you mention a collaboration with Dr. Leroy Apker at GE [David Dutton and Robert Maurer, “Color Centers and Trapped Charge in KC1 and KBr,” Physical Review, 90 (1953), p. 130]. His name has come up a number of times.
I don’t remember what we collaborated on there.
Let me see. (Flips through paper.) Oh, he supplied the cesium-antimony photocell.
Oh yes. We needed standard photocells, photocells whose quantum yield was known, and Apker had made those for his own work at GE and he in principle loaned one or two. In practice, of course, he gave them to us. They were essential to our work. Leroy Apker is a remarkable guy. We were graduate students together at Rochester. We were both students of DuBridge, and when I went to MIT, Apker went to GE. He got his degree a year later than I did, and at GE, he continued his work, on emission from tungsten, and he did it right for the first time. People had been studying tungsten since the beginning of the century, but he did the experiments right, both photoelectric experiments, and probably no better experimental job ever was done in physics. He eventually became in charge, went into the semiconductor area, and was in charge of much of their semiconductor research. He received the Buckley prize, in fact, he was either the first or the second awarded. That was principally for his work on tungsten. He was an unusual person, quite a loner. Didn’t marry until late in life, and killed himself while still young. A remarkable man.
Let’s see. There are a series of review papers that you wrote in the mid-fifties. The Colliers Encyclopedia article was written in the early fifties [Frederick Seitz and Robert J. Maurer, “Theory of Solids and Liquids,” Collier’s Encyclopedia, 18 (1952), pp. 19-22]. I had read this earlier several years ago when I was asked to do something like it for an encyclopedia of history.
I think what happened was that Seitz was always getting asked to do these things. And I think he had to go off on some trip, and he asked me whether I’d do it, and so I did it.
Let’s see, there’s an excellent review on imperfections [Robert J. Maurer, “Imperfections in Crystal Structure,” Record of Chemical Progress, 15 (1954), PP. 61-68] which for a novice like me is incredibly clear.
It’s very elementary.
I’d be very interested in learning how the work of Frenkel in ‘26 got started, and the Schottky-Wagner, and so on.
Well, there were an awful lot of people around in the fifties who were suddenly interested in impurities and imperfections in crystals, and there was a great demand for review articles, so that we were constantly being asked to participate in a symposium, or write a short article. Most of it, I don’t know, has no great interest, even I think historically. The field has moved way beyond that level of sophistication. It’s ancient history now.
But it’s interesting that, between ‘50 and ‘55, there was a surge of interest by a lot of people.
Was it the transistor that did it?
Oh sure, that had a tremendous amount to do with it. First of all, interest had been growing because silicon diodes and germanium diodes had been finding more and more applications. But once the transistor was invented, even people of modest ability foresaw that there was going to be a revolution in techniques. Of course, people were not only interested in silicon and germanium, they were asking themselves, is there anything better? So even a ceramicist, a metallurgist —remember purified silicon became largely a metallurgical problem, partly chemical and to a large extent, metallurgical problem. The great technique of zone refining was invented by Pfann, a metallurgist at Bell. But everybody was interested in defects, so there was a great demand for these things. Speaking of foresight, there’s a story that I must tell you. In the days of the war, maybe it was then, because I think we were at Chicago, but maybe not, one of my friends, George Valley at MIT, was called down to Fort Monmouth where the army engineers suspected that they had got an echo of the radar signal off the moon. Well, George went down, and he was the radar expert. He looked at their data, and said, “Yep, you’ve done it, you’ve bounced a radar beam off the moon.” Well, this word came to us, we heard about it, and you know, it was, in. a sense, it was sort of exciting that you get a radar signal out that far. And of course, at just the same time, German rockets, we were becoming aware of the technical advances of the Germans with rockets, the V- 2’s, in particular. And when a group of very distinguished physicists all of whom had been involved in the Manhattan district and the development of the bomb— a funny thing, when we were drinking together, I had just heard about the radar business and the moon, and coupling it with what I had heard about the rockets, I said, over a beer, “You know,” I said, “I’ll bet that within my lifetime we’re going to send a rocket to the moon.” And all of these people with very creative minds they jumped on me with both feet, and said, “do you realize what it takes to get a payload off the earth’s surface, orders of magnitude beyond what the V-2’s are like?” I said, “I don’t mean sending a man to the moon, I mean just sending a small payload, a pound or two of something.” And they said, “It’s out of the question.” (Laughter)
This was when?
Well, you could check back the date, but it must have been around ‘50. And these were people who had just come out of one of the most imaginative projects, where they had seen what was unimaginable ten of fifteen years before. And here, they couldn’t stretch their imaginations to include the development of rockets that would be capable of putting a payload on the moon. They said, “Oh, no, no, it’ll never happen.” I had forgotten, you know it was only ten years later or so, what was it?
It was late sixties when we got a man on the moon.
We had rockets in orbit long before that. So it was probably fifteen years or so. But it always impressed me how people who have shown the utmost imagination in one field find difficulty in transferring this to another field. .
There a few more little papers that we could discuss (thumbs through remainder of working file).
Well, these papers were very important.
Let’s then say a few words about them before winding up. For example, about the one on silver chloride with Dale Compton [W. Dale Compton and Robert J. Maurer, “Self-Diffusion and Electrical Conductivity in Silver Chloride,” J. Phys. Chem. Solids, 1 (1956), pp. 191-199].
Dale Compton. By the way, he’s Vice President for Research at Ford today, and in some sense, is one of my most successful students. This was a breakthrough in that we were able, for the first time, to measure the diffusion coefficient of a negative ion, not a positive ion like sodium or potassium, but the chlorine ion. And the results were exceedingly baffling when we compared the diffusion coefficient with the electrical conductivity. They didn’t agree, and we didn’t understand it. And just .at that time, two things happened: Bardeen and Herring published their data, their theory on the correlation effect. Alan Lidiard and a man named McCombie, who is now head of the department at the University of Redding, was here as a post-doc, and McCombie, I asked him to look at this discrepancy, and he knew of the Bardeen-Herring effect, which had just appeared, and he explained it to us, and so there’s a paper, which you probably don’t have here, by McCombie and Lidiard, which explains this data, it followed this paper. And, that was a great breakthrough, we actually could show that there was sense to this idea of a correlation coefficient, and then this paper was quite important although I must say people haven’t given it as much attention as I think it deserves.
This is the paper with Arthur Miller [Allan S. Miller and Robert J. Maurer, “Self-Diffusion and Electrical Conductivity in Silver Bromide,” J. Phys. Chem. Solids, 4 (1957), pp. 196-200].
Yes, in this particular case, we were actually able to measure very directly the correlation coefficient for vacancy diffusion in silver bromide and show that it agreed with the theoretical value. There have been people who made a whole career on this sort of thing since. There’s Bardeen and Herring [p. 196].
And then this number 10 is that [p.200] Lidiard?
(looking through paper) Compton and Haven, ah yes, McCombie and Lidiard.
Reference number 4 on the Miller-Maurer paper [p. 200].
This was the whole beginning of the experimental study of correlation coefficients in solids. I think those papers were very valuable. There was a man named Friauf at the University of Kansas who was taking data at the same time we were [Friauf F.J., Phys. Rev., 105 (1957), p.843], and unfortunately, we didn’t know about his work. It was just a gap. He was a little bit isolated, and he wasn’t quite ready to publish. We published before he did. I don’t know whether at the time he had the idea of what was going on, but his data was actually better than our data, because he’s a superb experimentalist, and the best data, I think, was Friauf’s. But we got in under the wire; if I had known that he was working on the problem at the time, I would have arranged to publish jointly with him. I was very embarrassed afterwards, it was just one of those, just didn’t know about it. But those are important papers in the history of the development of our knowledge of defects and diffusion in solids. The subject is of most technical importance in connection with metals, so that there’s been a great deal of work done on metals, and that tends to get a lot of the attention, but this work was the very beginning.
Great. Well, I’m going to stop at this point.
It’s a long session.
A long session. We are also at the place we’re drawing a line at for this particular phase of the project. It’s been a great interview. I learned a lot, and this will certainly be very helpful to us.
When you look back on it, though, mostly what you will see are missed opportunities. If we had only been a little bit smarter, if we had only worked a little bit harder.
That depends on one’s attitude. Thank you very much for spending all this time with me. I’m going to have these things transcribed and you’ll get a copy. You can then correct and change things around if you want to.
I don’t know whether I want to read all of that (laughter)....