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Oral History Transcript — Dr. Joseph Mayer

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Interview with Dr. Joseph Mayer
By Dr. Lillian Hoddeson
At Sanibel Island
January 24, 1975

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Joseph Mayer; January 24, 1975

ABSTRACT: Childhood and early education, Hollywood High School, Caltech graduate 1924 chemistry; to Berkeley 1924 with G.N. Lewis; postdoc at Berkeley for 1 Ĺ years working on statistical mechanics. To Gottingen (James Franck) 1929, marries Maria Goeppert; return to Gottingen 1932, works with Born on lattice energy calculations. Comments on work done with Maria Goeppert. Discussion of the application of the new quantum theory to solids.

Transcript

Hoddeson:

Iím interviewing Joe Mayer. This is on Sanibel Island. Weíre having a little after lunch conversation. Itís January 24, 1975, and this is Lillian Hoddeson. Iím very interested in what you started to tell me, just after I came back, when you were so pleased with the work that was referred to. (Weíre going to ramble, this isnít going to be a very structured interview.)

Mayer:

Yes. The discussion this morning was on solid state, and Iíve done some work in the field, long, long ago. Itís curious how I got into it. I got into it because of experimental tricks.

Hoddeson:

When was this?

Mayer:

Well, actually it started with my dissertation in Berkeley under G.N. Lewis, which I finished in 1927, and that was a rather difficult experiment. Actually, it was the first time, I think, that anyone had ever used an atomic beam in vacuum to try to measure the rate of the chemical reaction. Our stunt there was to run what was supposedly unimolecular reaction through a very hot tungsten-heated quartz cylinder, and to see whether radiation could induce the reaction. That was the common theory at the time, that so-called radiation theory, if you had a unimolecular reaction, it couldnít be due to collisions or it would be bimolecular. And well, we didnít get any reaction. So we called it disproof of the radiation theory. But the technique was something that sort of intrigued James Franck who was that year in Berkeley, and when I got a Rockefeller Fellowship and went to work with Franck, he suggested that I -- that was in, working in Gottingen, Germany, Physikalisches Institute. And that was in 1929.

I got there just about Christmas time. We sat up, actually I set up in a soft glass apparatus, and this was shocking because I was used to blowing pyrex glass, and the German soft glass was quite a problem. A hot graphite oven -- we heated salt, I think the first thing we did was iodide, or potassium iodide, heated it, and then had a higher temperature oven above it, and measured the emission of ions, from which you could calculate back to the vapor pressure of the ions above the salt. And with a little very simple statistical mechanics, you could calculate the energy difference between the salt and the ions. One had to check, because with a cycle, a so-called Born-Arbor thermodynamic cycle, the only thing that was unknown was the electron affinity of the negative ion. And with an experiment later we got the same value for the electron affinity of iodine from the two salts. So it was something of a check. That the method worked, and was correct. But then -- well, in the meantime, Maria and I got married, Maria Goeppert and I were at Hopkins, and when we went back, two years later, for the summer, I wanted to do something. Lindsay Helmholtz was now --

Hoddeson:

-- this is the summer of Ď31?

Mayer:

Ď32, actually. And a student of mine, my first student, Lindsay Helmholtz, whoís now at Washington University, went with us, and he and I worked with Max Born. You couldnít do experiments over a summer, then wasnít any sense, so we tried to do lattice energy calculations. Born and Arbor had done it, oh, about a decade earlier. And so we started to try and improve the calculations, and one of the things -- I donít remember whether Max Born suggested it, or whether I did, anyway, it seemed perfectly sensible -- instead of using R to the minus N, repulsive energy, we tried an exponential. We knew then should be an exponential decrease in electron density outside the ion, so that exponential looked more sensible. And then the other thing we knew then, which they didnít before, we had the London formula, for the Van der Waals [?] attractive potential, and of course we knew that that existed, because rare gas atoms also condensed as a liquid, so it must be an attractive potential. The attractive potential made quite a bit of difference, because whereas one had always assumed that the unknown potential, aside from Madelung electrostatic attraction, that the unknown potential went to zero from positive values, but if it goes to negative values and then up again, it makes quite a bit of difference in the energy. The idea was, you used the known density of the salt to get the lattice distance. You knew the crystal structure. You could calculate the Madelung constant, that gave the electrostatic energy, and then you used two -- well, you used this density to get the distance of the minimum in the energy. Then you used the compressibility to get the curvature of the potential at the bottom. So you had two empirical things.

Hoddeson:

When you say ďweĒ are you referring to you and Lindsay?

Mayer:

To Lindsay and Born.

Hoddeson:

Oh, Born. Maria was working on other things?

Mayer:

Maria was, at that time, I think -- was that the year? Iím not sure. Maria wrote a Handbuch article on lattice dynamics, with Born. Iím not sure whether it was that year -- it must have been that year, because I think the next time we went back, Born was leaving. I mean, Hitler had come in, the next time. And so we made -- of course, as things turned out, one of those things that always impresses me, it turned out to be extremely simple. I mean, here, with this exponential repulsion, it turned out that it had exactly the same form for all 20 alkalites E to the minus R over Rho, and Rho had the same -- I even remember the numerical values, 0.345 angstrom units. There was one bad exception, which was lithium fluoride, but it turns out that was bad experiments. They didnít have the compressibility correct. It had been done on an impure hydrate, on a hydrated salt, actually, I think. But there was one regularity, and the other regularity was the factor in front. You had, what was it, four heloids and five alkalis I guess so. So you had nine different ions, and you had 20 salts, four times five. And you could get the factor in front with nine constants. You simply put E to the minus, E to the plus, R over Rho for each of the two ions. You got good fit, for 20 salts. So it was quite -- it was fun.

Hoddeson:

Did you continue working? Maria then went to nuclear physics?

Mayer:

No, no, she really did quantum chemistry, from then on. We wrote a paper together on polarizability of ions, used the empirical, oh, one over R minus delta for the effective distance, which was empirical thing, where delta was the same for all states, I mean for all F levels. Then you could calculate -- the idea was that the ion and the F levels, high excited F levels, moved so slowly, the electrons, that it just polarized the ions, so that was the delta, and you could show it should be constant for all F levels, and use that value to get the polarizability. I mean, that was one of the few papers that Maria and I published together. Another one was on symmetry number in organic molecules, with Brunauer. But she worked largely with Carl Hertzfeld also on chemical problems. And then perhaps the nicest thing she did at that time was with Lee Sklar on the spectrum of benzene, which was one of the -- well, about the first calculation of the spectrum, electronic spectrum of a rather complicated organic molecule, and just on Debye-Hochel theory, putting together the Hochel orbitals, the excitations.

Hoddeson:

Did she have the kinds of problems that lots of women certainly complain of nowadays, about being a woman in a manís field? Did she do much complaining?

Mayer:

She didnít complain. She wasnít a complainer. No. She never got paid. Really.

Hoddeson:

She never got paid?

Mayer:

Oh, much later. I think Carl Hertzfeld paid her as a personal assistant something like $100 a year.

Hoddeson:

My God.

Mayer:

But I mean, I think that was probably out of his own pocket. But the university wouldnít. When we went to Columbia after --

Hoddeson:

-- did that have to do with the fact that she was married to you, or the fact that she was a woman? or both?

Mayer:

Probably both. Iím sure they had nepotism laws. They got her free, why should they? But Maria didnít complain. I mean, after all, sheíd been brought up in Germany, where it was worse for women probably at that time. At least it certainly was after Hitler. No -- oh, we had an awful lot of fun. I mean, science was so much fun. Thatís the main thingÖ (recording goes into fast gibberish here and then fades outÖ)

Hoddeson:

OK, this is better now. I can tell just by watching the speed. I use this thing so much that I can pick up every little complaint. You were talking about your daughter.

Mayer:

Oh, just that she was bilingual. She had Mariaís ability to do two languages very easily. I always find Iím completely fluent in German, but ungrammatical, but I have great difficulty translating, because the sentences in English come out Germanic in nature, of course. Maria, I remember, read to our son Kipling. We had it in German, and sheíd read it from the German book and come out in English with it, THE JUNGLE STORIES. I was amazed at that ability, to get immediately into another language, the ability that a translator has. Itís quite different than just knowing the language.

Hoddeson:

Sure. I would be interested in hearing how you got into science, got into physics, how you ended up working on your thesis in 1927, in the earlier part. I think we should probably start rather early, if youíd like to talk about when you were born, where -- about your parents --

Mayer:

I was born in New York City. My father was a bridge engineer. He worked on the Quebec Bridge, assistant chief engineer of the design of the bridge, the second one, not the one that collapsed. Then after the bridge was built, we moved to California. Iíd gone to schools in Westmont, and oh, up through the first year of high school, and then we lived in Hollywood for a while and I went to Hollywood High School, and I had a wonderful chemistry teacher. In fact I learned so much chemistry that after high school I decided to be a chemist. At that time, the price of sugar, just after World War I, was almost as high as it is now, so the sugar mills employed chemists, and some of us high school students worked a campaign in Huntington Beach, and then a campaign in Hooper, Utah, and then the price fell out of the sugar market. So two of us joined that last midyear class at Cal Tech where we started in February and then caught up with the people whoíd started -- that was hell, because we worked all through the summer and had no vacation. And the first two years at Cal Tech were not easy. But I guess we learned to work there, at least. Then I graduated from Cal Tech in 1924.

Hoddeson:

What did you major in?

Mayer:

Chemistry. And I did publish a paper, with [?], as an undergraduate at that time, on the free energy of aqueous sulfuric acid. I donít know whether I quite understood the paper, but D.P. Smith who was a post-doc at that time sort of took care of the mistakes in it. Then I went to Berkeley, worked with -- I was fortunate in working with G.N. Lewis, became he was remarkable. And --

Hoddeson:

Could you tell me about that?

Mayer:

Gilbert Lewis was -- well, he was the outstanding physical chemist of that period, and heíd been at MIT and gone to Berkeley. He insisted on being a dean, because then he didnít have all the bureaucracy above him, so they made a school of chemistry, and the Berkeley chemistry department is the School of Chemistry now. Itís not only a department, but the department with the chemical engineering is the School of Chemistry, so itís got less bureaucracy in it, or itís homemade bureaucracy, not imposed as much by the university, as the rest of us are, in other campuses. But Lewis was an extremely versatile and very brilliant man. He worked on everything, from relativity to -- his book with Randall on thermodynamics was the standard book for all chemists at that time. But there were no graduate courses at that time in the chemistry department. We had to take courses in physics. But there were no regular graduate courses in chemistry. There was a course in thermodynamics that I didnít have to take because Iíd had it under Tolman at Cal Tech. But many of the entering graduate students had to take that course, but it was an undergraduate senior course. There were often lectures given. Some member of the faculty would get interested in something and heíd announce that he was going to talk every afternoon at 4 oíclock on some subject, and heíd do it for two weeks, finish the subject, but it was never a course, as such. It was never in the catalog. It just sort of suddenly appeared on the bulletin board, that someone would talk about some subject.

Hoddeson:

When did you enter graduate school?

Mayer:

Ď24. In the autumn of Ď24.

Hoddeson:

Were you aware of the great developments that were going on just at that time, the mysteries that people were working on in Germany?

Mayer:

Yes. Yes, you see, at Cal Tech as an undergraduate under Tolman, Ehrenfest spent a year at Cal Tech, I donít remember whether it was Ď23 or Ď24, and Tolman was also someone who was -- he gave a course, as a senior I took a course from Tolman on atomic structure, and Sommerfeldís Atombau was the textbook. I remember, I did miserably, because the course had Paul Emmett in it as a graduate student, and Linus Pauling, and Dick Banger[?].

Hoddeson:

They were graduate students?

Mayer:

They were graduate students, and I was an undergraduate student, and I was, I think, sort of mentally underprivileged, compared with them. But it was fun, and of course, although I was relatively stupid in the course, I still learned quite a bit. Enough so that the second time around at Berkeley, I began to understand some things.

Hoddeson:

Who was teaching it at Berkeley when you took it again?

Mayer:

Well, this was mostly in seminars and private conversation. Oppenheimer came back for half a year from, where had he been? Heíd been in Gottingen, I think. That was about 1927 or Ď28. Itís funny, in the biographies written about Oppenheimer, no one ever mentions that he was back for that half semester, that semester. Itís always -- I mean, Iíve noticed -- I know he was there, because I took the course with him. Ed Condon was in the physics department, and he gave the course in vector analysis, which was very difficult because it was 8 oíclock in the morning, and that was sort of hard to get up for.

Hoddeson:

So you were learning I guess Hamilton Jacoby theory in order to do the calculations that Sommerfeld was talking about in Atombau is that right?

Mayer:

Yes.

Hoddeson:

And you were working with the correspondence principle, I gather, in order to calculate -- (crosstalk)

Mayer:

Well, in Die Atombau of course, actually --

Hoddeson:

It wasnít formulated there?

Mayer:

It wasnít -- no, I was trying to learn; it, I wasnít doing anything.

Hoddeson:

Iím trying to get a good sense for what you were learning, in physics as well as chemistry.

Mayer:

Not very much. G.N. Lewis always tended to say, ďDonít study it out of books, do it yourself, make it up.Ē He claimed that he had never had a course in mathematics beyond simple algebra. Heíd invented calculus for himself, so to speak, and -- he was a good mathematician, but I think that is one of the things that the Berkeley chemists got quite characteristically. They were not, did not tend to read the literature in great detail. They tried -- it was very successful, because of that period, of people of that age, a very large fraction of the members of the National Academy, Physical Chemistry, came from that, from Berkeley. It isnít that we knew things, but we were used to working and used to doing -- doing science as fun. We enjoyed it. I did work, after I got a degree I worked for a year and a half with G.N. Lewis, and we tried to understand statistical mechanics of that time.

Hoddeson:

How did you go about doing that?

Mayer:

Weíd meet after 9 oíclock in the evening, and work until G.N. got tired, which varied between 11 oíclock and half past 1, depending on how excited we were getting.

Hoddeson:

What texts were you working with?

Mayer:

No texts. No, no. Weíd simply heard about the Boze [?] paper -Ė Boze-Einstein on black body radiation -- and at that time, the -- somehow, we knew about the Fermi-Dirac statistics. I donít remember. But well, you didnít have to know much. I mean, there were particles, you could only put two in the quantum state with -- letís see. We only knew two in the quantum state. We didnít have electron spin at that time, did we? No, that came later.

Hoddeson:

No, I think that came about that time. Didnít electron spin come in Ď25, Ď26? Fermi-Dirac paper?

Mayer:

Yes, Iím sorry, Iím wrong, because this was Ď27. No, no, we had the electron spin, very definitely, of course. Of course.

Hoddeson:

You canít get Fermi-Dirac statistics -- yes, you can --

Mayer:

Well, after all, Pauli, you see -- I mean, made the periodic system, with two electrons, without knowing why ďtwoĒ in each orbit. No, G.N. and I published, I think it was three papers in the National Academy on the derivation of the laws of thermodynamics from statistical mechanics, and on the Boze-Einstein-Fermi-Dirac systems, so I knew a little statistical mechanics, before I went to Gottingen, but I didnít work on it again till Hopkins. That was when Maria and I decided to write this book, and somehow I got diverted trying to understand the Verial [?] coefficient thing, and made this cluster work at that time. You had, Philip Ackerman was a student of mine at that time. He and I worked on it together, and then Sally -- Sally Harrison, who became Sally Deka, married Gerard Deka, took a degree with me in that Ė- on cluster expansion.

Hoddeson:

Well, Iím going to stop you for a second to turn the tape over.

Mayer:

I donít know whether it tires me -- except that I get annoyed that so often I remember wrongly. This business with the 1927, whether we had electron spin.

Hoddeson:

Thatís very difficult to remember, itís many years ago.

Mayer:

Yes. I place the time -- I mean, I was thinking of an earlier time, but it was after Ď27, because I got my degree in Ď27.

Hoddeson:

How did you happen to go to Gottingen?

Mayer:

Well, James Franck had been for a year, or a semester, Iím not sure, in Berkeley, and quite a few of the people from Berkeley, from the chemistry department, had gone and worked with him. Hochness had been there, Ernest Gibson, who was part of the faculty, was not a German but heíd married a German wife and they went back quite often, and he knew of the Gottingen group. Somehow Gottingen was the place to go at that time, and I got this Rockefeller Fellowship, I went there. Who else besides [?]? There were others that I spoke to, that had been there. I asked where I should live. I mean, what you did about living. And he said well, there were two pensions, [?] was one, Cario was the other, and most of the Americans stayed at one of those pensions. And he said, ďWell, if you can get a room in a private house, itís much better.Ē ďNow, Professor Goeppert died last year, and I think Frau Professor Goeppert has one or two rooms for rent. Itís a good place to go. Besides, he has a very pretty daughter.Ē So when I went to ask Franck what I should do, he said, ďPossibly thereís a room at Frau Professor Goeppertís.Ē So I went and rang the doorbell, and a pretty little snip of a girl came to the door, and wouldnít talk German to me. Her English was perfect. But Mutter Goeppert had a terrib1e cold at that time. However -- oh, Milliken had had a room in the Goeppert house, before. Apparently Milliken had left a good enough reputation for the American scientists so that I was given a room.

Hoddeson:

At what stage in her scientific career was Maria when you met?

Mayer:

Maria was really just about starting her dissertation work. She -- well, we married in January, 1930, because Mutter Goeppert had come to the conclusion that Maria would never get her dissertation done unless she got married. Maria got her degree in the middle of March, I think, actually, took her exam.

Hoddeson:

Iím trying to get the dates a little bit clear. You arrived in the fall of Ď29?

Mayer:

In the fall, or perhaps already in 1930, but about the first of January. Iíd asked, what was his name, Tisdale, who was running the Rockefeller Fellowships at that time -- they had rather strict rules that you had to work 11 months a year, and I didnít like that. Actually, it was kind of ridiculous, because the laboratory was literally locked for about three months, and so I had asked that Iíd like to stay for 15 months, and then be permitted to be absent, take vacations. So that was granted, and so, I did a little traveling in Europe, and of course went to scientific meetings.

Hoddeson:

Where did you go? This helps me because Iíd like to know, where are the places one would stop if oneís visiting Europe at that time.

Mayer:

It was somewhere in the Harzen -- when I say I went to scientific meetings, I think actually there was only one meeting of the German Physical Society that I attended. It was in one of the Harz Mountain cities, Iím pretty sure. I remember, I got on the train, quite a number of the students were going. Maria came down to see us off, and we said, ďYouíd better come,Ē so she got on the train and went to the meeting with us. I donít remember much about the meeting, really. But I remember lots of fun with the students. At that time, of course, the core students, the equivalent of the fraternities, were very popular, and every Wednesday, the core students would go out in big four horse, or were they only two horse drawn wagons, to a place about five or ten miles outside of Gottingen known as Maria Spring, and a respectable girl could go, in the afternoon, but she had to take the 6 oíclock train home, because after that, she was no longer respectable! It was generally beer drinking, lots of singing, a band, dancing, -- it was a very lively sort of life with the students. Of course, they dueled. There were some other Americans there at the time -- Watts -- Watson, Weimans, excuse me, who was University of Wisconsin. Iíve run out of memories at the moment.

Hoddeson:

Did you attend seminars at Gottingen?

Mayer:

Oh, yes.

Hoddeson:

Or were you mainly working on your own?

Mayer:

Oh, no, they had a seminar.

Hoddeson:

-- who --?

Mayer:

-- well, Frank and Pole. Pole was an estes physicologist. He mostly did solid state work. Hilch was his assistant. Arthur Oldenberg was there at the time.

Hoddeson:

Did they call it solid state at that time already? This was very early.

Mayer:

I think they called it solid state. I donít know what they called it. I mean, they called it in German, whatever it was, but it was -- it was all on crystal physics, and Born -- well, Born, Franck and Pole ran the seminar. Hilbert came quite often. I donít think Courant went. We knew Courant very well. Of course Maria, having been a professorís daughter (he was professor of pediatrics) as well, the Goeppert family knew all the professors, of course, and Courant was at the house very often, Born. Dr. Oldenberg was with Franck and of course, Hertha Spooner and Cario was an assistant then of Franck, and L.A. Sommer was there. But I donít think itís appropriate to tell the story of Sommer.

Hoddeson:

Do you want me to turn off the tape recorder?... OK, weíre recording now -- I would like to know, a little bit about how, if you know, how the work on applying the new quantum theory to solids began in Gottingen and other places. You came just after that had already begun. Was that a natural thing to do, to immediately -- once quantum mechanics had been developed as a tool, was it natural to immediately apply it to solids, or was that a special interest of Bornís?

Mayer:

Actually, I think Bornís work was very classical, as applied to solids. I mean, it was, what? -- I mean, the lattice energy calculations, for instance, were essentially purely classical. It was just an empirical repulsion between ions. The lattice dynamics, all right, you quantize the energy levels, but the problems were essentially classical. The stress, strain calculations -- I donít think it was any more quantum mechanical than -- well, than pre-1920 quantum mechanics. I mean, there were vibrational levels -- all right, they didnít have N plus a half, in pre-1920.

Hoddeson:

He must have been aware of the work of Sommerfeld, that preceded his.

Mayer:

That of course, but I meant -- of course, the Sommerfeld group that did the metal theory, of course, that started with Drudeís success in getting the ratio of electrical to thermal conductivity, on electron gas theory.

Hoddeson:

Yes, except that of course that had been done much earlier.

Mayer:

That had been done much earlier, yes, but that -- it, so to speak, didnít make sense, because the mean-free paths -- I mean, letís see, what was the difficulty? In the first place, you had the heat capacity difficulty. There was no heat capacity due to the electrons. So there had to be very very few electrons. And then the mean-free path had to be so enormous that you couldnít believe that, on the classical, semi-classical theory. So it wasnít a comfortable theory, although, until Sommerfeld applied Fermi-Dirac statistics to it.

Hoddeson:

But that couldnít have come about if it hadnít been for the new quantum mechanics.

Mayer:

Well, that, certainly. But when I said Born, you had mentioned Born -- his work, I think --

Hoddeson:

-- was quite different.

Mayer:

Was quite different, wasnít particularly applying quantum mechanics, it was classical. And I donít know much about Ė- I wasnít concerned personally, so to speak, of the developments of the Bloch waves, -- all right, I taught it in class, but, I havenít any, I donít know enough about what motivated people at a particular time, and where they --

Hoddeson:

That had some connection with Heisenbergís work. I havenít studied this in detail yet myself, but my impression is that Heisenberg got interested, and Bloch was his student, at Leipzig, and then he took off.

Mayer:

On ferromagnetism? Or?

Hoddeson:

Well, I donít know, I havenít worked that out yet. But anyway --

Mayer:

Of course, Heisenbergís I guess was the first reasonable explanation of the ferromagnetic interaction.

Hoddeson:

What I donít know is whether Bloch worked with Heisenberg on ferromagnetism, or whether it was some related problem, or something quite different.

Mayer:

I think it was quite independent. But Iím not sure.

Hoddeson:

But I was wondering whether Born and Sommerfeld were in touch with each otherís work at that time.

Mayer:

Oh, Iím sure they were in touch with each other, but I donít think there was anything that youíd call collaboration. Of course, Heisenberg had been in Gottingen, and he came back quite often and visited. Born had two grand pianos, back to back, and I remember one evening, Born and Heisenberg playing double piano, duet -- it was quite impressive. They were both very good pianists. Yes. I have -- had never seen two grand pianos back to back; I think I never have since, except on the stage.

Hoddeson:

Thatís a very grand home.

Mayer:

It was an apartment, but good-sized rooms.

Hoddeson:

Did Born have many students at the time?

Mayer:

Yes. Yes. I guess, -- oh, Iíd hate to give a number. There werenít many compared with present day numbers of students, but there were quite a few.

Hoddeson:

Were they more like two or five or seven?

Mayer:

I should say five. Of course in a sense -- everyone who worked in theoretical physics worked with Born. I mean, including the Privatdozent, so to speak. It wasnít that anybody worked just with the Privatdozent. It was, the professor -- the students always worked, so far as they worked with anybody, with the professor. Did Per-Olov-Lowdin ever tell you the story of his dissertation with Waller? You can ask him now he wants to correct it, but I first knew of Per through listening to a talk that Waller gave in Chicago on Perís work, on this three body explanation of the Cauchy relations in crystals, and when I met Per, I told him that, and he seemed to be a little surprised that Waller had, so to speak, traveled the United States talking about his work. Then Per told me that in about 1939, I think, heíd gone to Waller for a problem, and Waller had said, ďWell, why not try to work on the self-energy of the electron?Ē And if I remember Perís story, 1942, he went back to Waller and said, ďI canít Iím just not getting anywhere.Ē And Waller said, ďWell, why not try and explain the failure of the Cauchy relations?Ē So Per went away and he came back, three years later, with his dissertation. And Waller said, ďMy God, I didnít think anyone would ever have solved that problem!Ē I like that story. You can ask him, tell him that Iím repeating what I think he told me.

Hoddeson:

I will ask him about that. Iím interested in Cauchy because heís one of the figures in the period Iíve just been Ė-

Mayer:

I beg your pardon?