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Oral History Transcript — Dr. Emanuel Maxwell

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Interview with Dr. Emanuel Maxwell
By Gordon Baym
At Francis Bitter National Magnet Laboratory, Massachusetts Institute of Technology
March 4, 1983

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Emanuel Maxwell; March 4, 1983

ABSTRACT: Mainly concerns Maxwellís work on superconductivity and specifically the isotope effect experiments. Discussion of Maxwellís experiments on superconductivity in tin, his work for the Massachusetts Institute of Technology Radiation Laboratory during World War II, the effect of the war on superconductivity research, and then details of Maxwellís experiments on mercury and tin.

Transcript

Baym:

I am now visiting Dr. Emanuel Maxwell at the Magnet Laboratory at MIT. Lillian Hoddeson gave me a collection of questions to ask you.

Maxwell:

Sure.

Baym:

To begin with, how did you become interested in research on superconductivity?

Maxwell:

That started in my graduate work at MIT.

Baym:

Was that your thesis?

Maxwell:

Yes it was. You see, I was in the Radiation Laboratory during the war. I came up in November 1941, just before Pearl Harbor. My background had been electrical engineering; I had done my undergraduate work in engineering.

Baym:

Where was this?

Maxwell:

At Columbia. And I at that point was out several years. In fact I had gotten my last degree there in 1935 and spent some time working in various things, eventually several years working in applied geophysics physics for the Shell Oil Company. And when the Radiation Lab was in operation, one of the scouts — Tom Bonner — came out to look for people and he knew somebody who I knew, so we got together and I got hired. And I came up to the Radiation Laboratory and worked there from November 1941 until the end. And the last several years of my stay there I spent in Ed Purcellís group. One of the problems, in fact the last problem he assigned to me, was to look at microwave conductivity because some of the early data that they had on effective conductivity at frequencies of 1 cm was — there seemed to be an anomaly there. So the question was: is it a basic anomaly or was it simply an artifact?

Baym:

This is right after the war?

Maxwell:

No, this is during the war. We did a lot of actual basic research in the Radiation Laboratory in those years. As a matter of fact I think that contributed a lot to the things I became interested in later. And so I worked on that problem for maybe the better part of a year, I canít remember. What I found was that basically there was no anomaly. People just didnít measure DC conductivity of the material properly enough. And often this was the case. But there was a small correction which I finally decided was due to surface roughness, and I think I sent you a copy of that paper that was published. It was originally a Radiation Lab report.

Baym:

This is dated January 15, 1946. Was it worked on earlier?

Maxwell:

The work was actually done actually in the Radiation Lab during the war and then the material appeared as a Radiation Lab report. I donít remember if I sent a copy of that or not.

Baym:

I have here the technical report but this is —

Maxwell:

That appears to be a journal —

Baym:

This is all there was from this early period.

Maxwell:

Okay, I can dig one out. There originally was an internal report of the Radiation Laboratory in 1945 describing that work. Anyhow so I had developed a lot of techniques for measuring attenuation in waveguides and Qís of cavities and that sort of thing. And so I probably was something of an ďexpertĒ in that area. And then at the end of the war when MIT went back to do its ordinary business they organized a research lab in electronics and a lot of us wartime people — a couple of handfuls, at least — were integrated into that. I think we were people who didnít have Ph.D.ís at that point, so we were going into graduate studies. It was I and people like Woody Strandberg, and a whole bunch of people all in the same class. And coincidentally at the end of the war or during the war Professor Sam Collins in the mechanical engineering department was working on methods of refrigeration and liquefaction. And in the latter part, sometime in the latter part of the war, he was perfecting his Collins cryostat. So there was a natural idea to bring these things together. Of course, Slater was the organizing factor here. He got together in the research laboratory of electronics a group of students who were interested in the sort of things he was interested in doing, and one of these was to look into microwave superconductivity.

Baym:

Did you say Slater was responsible for going into low temperature?

Maxwell:

Yes, Slater was. There was a guy named Bestar at that point. Slater had become something of an experimentalist during the war. Nobody knows that.

Baym:

I didnít know that, no.

Maxwell:

You see Slater very early got involved in Radiation Lab problems and he became involved in the magnetron problem. That, after all, was a natural step from his work on calculating atomic orbitals and solids and that sort of thing, and he went from one periodic system to a much simpler system, but one which was much harder to characterize and to analyze actually. And so, somewhere during this period, he decided he had to do experimental work. And so he went down to Bell Labs and worked at Bell Labs for a while during the war doing experimental probing and the resonances of these multi-cavity magnetrons and he developed a good experimental feel for microwave systems. And when he came back, this is one of the projects he became interested in. The other one was the electron accelerator. Again you can see the relation.

Baym:

Microtrons?

Maxwell:

Not microtrons, it was the — well, I donít know whether the microtron is something I associate with another device. This was the chain of microwave cavities through which you focus an electron beam. Slow wave structure, in other words. Itís been so long that Iíve thought about these things, that I have to get back in gear. So he was really supervising two experimental projects. One of them was the construction of this electron accelerator and the other was the microwave superconductivity work, which was a sort of union of the microwave know — how in the electronics laboratory with the cryogenic knowhow of Professor Collins. And we worked — John Garrison, who was another Radiation Lab alumni, and I worked together as a team starting out in the fall of 1945, trying to build a system to observe superconductivity at liquid helium temperatures. Actually started out with a lead cavity. Lead is what we knew about. We were actually very [???] about low temperatures in those days. Well, I can see I can just talk all day about that particular...

Baym:

Iíd be delighted.

Maxwell:

But it was a team which consisted of John and I as the graduate students and of course Slater was over there over all and experimentally it was Professor Collins and I think Howard McMahan, who later went to Arthur D. Little, was his graduate student, and a technician by the name of Bob Cavalier, who was a great guy. Francis Bitter was also involved in that, and Charlie Squire. And that was in getting the initial experiments going, and later some of these people split off into other aspects of low-temperature work. But we worked at this for a few years and did our experiments which were rather crude and which were published. I donít know whether John Garrison was a little bit further ahead in his course work than I. He got his degree the year before I did in 1947. I donít think he ever published his thesis which was on the superconductivity of lead at 11/4 cm, and I went on to investigate tin. And of course we did these things in what seems like a terribly crude way these days. We hadnít acquired the technology of transferring helium out of a cryostat into a Dewar; we did all of our experiments in the machine, in the Collins machine, which was banging away.

Baym:

What motivated your interest in tin?

Maxwell:

Well, you see the reason for working with lead was that I think that the transition temperature of lead was 7.2°. I donít know whether Collins had yet gotten down to liquid helium temperatures or just barely down there once or twice, but we were putting a heat load on the system, and we felt that we had a better chance of seeing something if we didnít try to shoot for lower temperatures. So, of course, lead was easier to do in that sense; we could see the superconductivity without getting down to actually liquefying the helium. But of course you had no way of stabilizing the temperature and that in addition to mechanical vibrations which didnít help much. But we actually did it on a transient basis; I remember with great excitement the first night that we actually were looking at the resonance of the cavity. We swept, frequency swept down the oscilloscope and I remember we finally got the darn cryostat to work so we got down low enough. And we saw all of a sudden there would be a resonance going up on the screen. It was quite an exciting thing. It was such a novelty in those days that all the senior people would come around to look, like Stratton, who was the director of RLE [The Research Laboratory of Electronics] then, to observe this unique phenomenon. You must remember at that point the number of laboratories on the North American continent where helium had been liquefied were very few. I think in Toronto, they had liquefied helium. I think Lane had at one point. Yale and Bureau of Standards in Washington had done some work, but that was it. So this was all very new. Well, the reason for going on to tin was that after we started going on this we had some contact with some more knowledgeable people in low temperatures; in particular I remember Gorter came over and visited here. He spent a semester at Harvard and gave some courses on paramagnetic relaxation.

Baym:

Do you remember when that was?

Maxwell:

That would have been probably about Ď46, Ď46, or Ď47.

Baym:

That early?

Maxwell:

Oh yes. It was a semester — we can research this — he was in residence at Harvard at that time and I remember he did give a series of lectures on paramagnetic relaxation. Anyhow, he gave us a little advice and it was clear that since by that time we had already gotten down to 4.2į and were liquefying helium we would have a much more controlled experiment if we went to tin which we did. But of course the technique of making these resonators was really in a sense crude. It was no small trick to actually make a system that was vacuum-tight that you could couple the vacuum into and couple the microwaves into. And we made these cavities. John Garrison and I after some rather discouraging initial tries finally made some by pressing in an arbor press with a tool and this was a very effective way of making a cavity. Unfortunately it turned out that we put a certain amount of cold-work in the tin and we had residual losses that a more careful approach would have eliminated.

Baym:

Did that spread out the transition temperature also?

Maxwell:

No, I doubt that it spread out the transition temperature, because the transition temperature at microwave frequencies is really broad anyhow.

Baym:

Yes, thatís right.

Maxwell:

Because the normal electrons participate in the process at high frequencies, so the breadth of the transition is really a function of the penetration depth, the superconducting penetration depth at those frequencies, at those temperatures. You did observe a residual resistance, when you extrapolate to 0į K, and of course that you should not have, and so that if you subtracted out the residual resistance you could then use the data. And of course some of the people with a better low-temperature experimental tradition managed to avoid that. The original high-frequency work experiment was done by H. London before the war using pre-war techniques and it was really a masterpiece of experimental achievement considering what was available then. And then also at the time we started, Pippard at Cambridge was —

Baym:

I was going to ask you what the relation was between you and the other American groups.

Maxwell:

It was independent to start with but then of course we rapidly began to communicate with each other.

Baym:

There was also Fairbank at Yale.

Maxwell:

Well, Fairbank was another Radiation Lab alumnus. How Fairbank got started I donít know. It was probably just natural for him to be involved in that when he went back to graduate school, taking with him a background in microwaves to Yale where Lane had some tradition of low-temperature physics. So I imagine it came about in the same way. And Pippard, well the first information we had about that was a letter which was published in the Proceedings of the Physical Society showing his results at something like 1000 megacycles, and he came to it probably in much the same way. During the war, he told me, he had worked for one of the British Ministries of Services involved in radar work and worked with Mark Rosenfeld. He had an equivalent technology, and when he went to Cambridge he had the advantage of course of working in the Mond under Shoenberg in a laboratory which was established by Kapitza in which they had a respectable tradition and experience in low-temperature physics. Whereas we had all started out fresh and had to learn a lot of things.

Baym:

Had you visited the Mond?

Maxwell:

Not before. I have since several times, but I had not at that point and I didnít meet — well letís see, Gorter did come through to MIT rather early. It was probably about Ď46, Iím sure it was about Ď46, and a couple of other people. Deosorgne, a Belgian who had worked in Leiden and also came and spent some time with us. But then Iím trying to think of the various visitors we might have had. One of them I do remember is Ogg. Do you know the story of Ogg, a chemist from the University of California; this was again about Ď46 or Ď47. He was a physical chemist who had done some work with frozen alkali metal-ammonia solutions which are very highly conductive at liquid nitrogen temperatures, and he claimed to have observed superconductivity in sodium ammonia solution at liquid nitrogen temperatures.

Baym:

Really.

Maxwell:

What he did was an experiment in which he seemed to be able to induce a persistent current. He had a theory in terms of Einstein pairs of electrons, and it was very interesting.

Baym:

Remarkable.

Maxwell:

Remarkable. On the basis of this, I think he eventually got a promotion. I donít know where he was, University of California, or Southern California. But immediately probably half a dozen different laboratories jumped in to try to duplicate these results and no one could duplicate them and his results were discredited. I think he suffered a nervous breakdown in the process; he was very highly strung up. I think it came to a sad end because of that. Anyhow, he was the only other person I remember.

Baym:

I would like to ask a general question on the impact of the war on solid state physics and this work. You mention that you were doing this as pure research.

Maxwell:

Yes, during the war it had a practical aspect to it in the sense that first of all because it was war we wanted practical information; we wanted the attenuation of various metallic systems. The other thing was there was a certain amount of basic research done which had a sort of mixed motivation. I mean mixed in the sense that after all there were a lot of physicists there who liked to sneak something in if there was some kind of justification that you could make for it. I mean obviously in the MIT Radiation Laboratory we couldnít justify nuclear physics like you could at Los Alamos of course. But there were various things that were investigated like atmospheric absorption, the oxygen line. Dickey started that. In fact the Dickey radiometer is something he developed in the Radiation Laboratory. And there was work done on the dielectric relaxation in water in the microwave range. Part of the people in our group did that under Ed Purcellís direction, and the reason for doing the investigation in microwave attenuation I think was a mixed thing. I mean there was a practical aspect to it, and if there really was a fundamental phenomenon there we certainly wanted to know about it.

Baym:

What about the Collins liquefier?

Maxwell:

That was something which Collins was again, in his prime, he was working on this before the war, I believe. And during the war he got involved in developing liquid oxygen machines for the Air Corps, the Air Force and the Army. And he developed the work, machines that were very portable that could make liquid air very rapidly in the field. He had been interested in very low temperatures before the war and how he, under whose auspices the first Collins cryostat was (? 293), Iím not sure. I think it was probably the Air Force and what the justification for that is, who knows? Certainly liquid helium was not their interest at that time, but somehow it got started under government sponsorship. And of course it was a great impetus to solid state work right after the war. Charlie Kittel spent a year or two at MIT at the Research Laboratory of Electronics.

Baym:

Can you think of any other examples of the impact of the war on superconductivity research?

Maxwell:

I would say there were two areas that I could think of are those that Iím familiar with. One of course is the development of the Collins cryostat, which really made low-temperature physics possible on a large scale. And the other was the microwave superconductivity problem. There probably are other connections, but theyíre probably less than direct. I think what happened during the war was a lot of people went into war work and acquired a lot of technology as a result of that, which they were then able to apply to their civilian work when they went back to it. That happened on every level, of course. For example, the paramagnetic resonance is something which was able to go ahead because of the development of microwave techniques during the war. In fact, I remember when Zavoiskeyís first letter came out, I think it was in JETP, and Charlie Kittel got very excited about this, and he was looking for some experimentalist to do work here. In fact, Arthur Kip is the man he drafted and that was very successful.

Baym:

Letís turn now to the isotope effect work. Now in your original letter that you sent to Physical Review, you say (looks for letter) in the first paragraph, ďthe existence of a small quantity of mercury-198 of the Bureau prompted us to investigate its properties as a superconductor.Ē How did you come to do the experiment?

Maxwell:

It started something like this: I had arrived there in June of 1948 right after I got out of MIT. And my plans were to continue some of the microwave work down there. But of course they had no microwave equipment and we started to get some and it took a long time to get going and meanwhile I was thinking of something else that would be interesting to get involved in, and I read about the use of mercury-198 as a spectroscopic standard. And it occurred to me well why not try this and see? When I spoke to Lillian Hoddeson on the phone a few weeks ago, she asked whether in the beginning there was any specific intimation it might be a phonon interaction.

Baym:

Yes.

Maxwell:

Originally, no. As a matter of fact, we werenít thinking in those terms. You must remember that what we knew about superconductivity then was essentially thermodynamic properties and also the London phenomenological theory. That was about where it stood. Unless you were tuned into a very specific way of looking at a problem, you just donít latch onto it. Anyhow, continuing historically, in those notes I sent your wife I think the first notification of what I had was sometime in 1948.

Baym:

I have that here. Itís the one from which you took the Xeroxes. [Pages from Maxwellís notebook indicating first ideas on isotope effect, Nov. 18, 1948, Dec. 13, 22, 24, 1948, April 25, 1949.]

Maxwell:

And I thought of this and I mentioned it to our division head, Brickwedde. I remember it was at a party that Russell Scott, who was chief of our section, was told this and I told him Iíd been doing this and he said ďwell, why not?Ē ďAs a matter of fact,Ē he said ďjust about a week or two ago I was talking to Herzfeld, and he suggested that maybe somebody ought to look at some of the uranium isotopes.Ē You know, uranium was a superconductor. He knew that uranium isotopes were separated and the reason he suggested it was that he had come from a meeting in Europe sometime that summer at which Pauli was present. And they were discussing superconductivity and people were putting forth what their ideas on superconductivity were.

Baym:

This is the summer of Ď48.

Maxwell:

This is the summer of Ď48, and Pauli made a remark. You know, it was just one of these remarks that people make; it was probably nothing more than that. But he didnít think that they were going to get anywhere unless they looked at the effect of the lattice in superconductivity. So as far as I was concerned probably this was the first conscious impression of mine with regard to the lattice. Even so, it didnít really take in a significant way. So that we got together with Herzfeld and we had some discussions about the experiment.

Baym:

Were you at this meeting?

Maxwell:

No I was not. We just heard of the remark from Herzfeld, who had been at this meeting. And we talked about ways of doing this experiment, so I set about to try to do it. First of all, I had to get permission to get some of this valuable mercury; there wasnít much of it. And I was very cautious about how to handle this. I was afraid I might break the capillaries or something like that and there goes the mercury and my name is mud. The other thing was that I thought probably the surest way to look for the effect would be to make a resistance measurement, because, if you saw the resistance go away then you knew it was superconductivity. Some of these other inductive techniques, maybe they would work and maybe they wouldnít, but I had no experience with them. And the other thing was that what we did know was that you had to be very careful about the physical condition of a specimen. It should be pure. It should be a single crystal, if you could possibly do this. We were obsessed with all of the thermodynamic rules that had been laid down by the experts in this field. So sometime shortly thereafter, I started to investigate the possibility of doing this by resistance and to work at first with some dummy natural mercury samples. First of all I had to get this mercury and distill it into a capillary and seal it off, and I spoke to all of the authorities in the Bureau there about purity, the chemists about how to clean the glassware and how to do the distilling and so forth. I remember getting the glass blown and getting several of these gadgets made which I show a sketch of for distilling the mercury into the capillary. And then I set this thing up, and in order to clean it I was going to have to pump or pull, suck some cleaning acid through the thing and rinse it carefully and trickle distilled water. All of those superstitions you feel are necessary when you start out in a totally unknown field. The other thing is if there was an effect we didnít expect it to be a very large effect for this reason: in earlier years there were experiments done on lead isotopes by Kamerlingh Onnes in Leiden and by Justin in Germany and they could see nothing. And so we felt that if there was an effect, it was probably small and we would have to have very good temperature resolution in a very faint system. So I set to work to clean out these capillaries and I remember this incident very clearly. I was trying to suck this nitric acid or combination of nitric and sulphuric through the capillary in a vacuum and it was going very slowly and I stood there looking at it and I was called to a telephone. So here I was, this apparatus was sucking away and I went to answer the telephone and all of a sudden I heard a big crash, a big explosion. What had happened was that the darn thing exploded sending glass and acid in every direction and if I hadnít been called to the telephone I would have gotten a face full of God knows what, so at that point I gave up my technique and I went back to thinking about an inductive technique. In fact I had probably earlier — the chronology escapes me now — I had investigated a, letís see, in 11/48 I describe the apparatus. I donít talk about the experiments but then in December I think, probably before I did the first fatal experiment on the capillary, I investigated some AC methods. In fact I know that was at the end of 1948, and then some time — it was in 1949 — some time went by and I didnít get on with this. In retrospect I should have, but of course no one ever knows, and the things you imagine you have to be very careful about it turns out you donít have to be very careful about at all. I remember that in 1949 it was after the second International Low Temperature Conference at MIT, which was held in the summertime, we had some visitors come down from Washington at the conference. One of them was David Shoenberg, and I showed him this inductive apparatus. I told him about this experiment — I hadnít done it yet — and what I remember very clearly, itís amusing now, he said, ďwell, one thing Iíd like to caution you about is freak experiments. (Laughter) You want to be very careful about getting the temperature measurement right,Ē and he clued me in all the things you had to do to be really careful to avoid seeing an artifact which you would then interpret as a real phenomenon. I had a little experience with that so naturally I was rather cautious. And so I, for one reason or another somehow didnít get around to doing the isotope experiment until the beginning of 1950. And then of course I abandoned all the things I thought about before. I decided to do a simple ballistic galvanometer technique to do it.

Baym:

Can I back up for a moment?

Maxwell:

Yes.

Baym:

Coming back to the notebook here, the style with which you wrote the notebooks is very strange.

Maxwell:

Itís rather discursive, is that what you mean?

Baym:

Yes. What was the reason for that?

Maxwell:

The reason for that I think was probably two-fold. Number one, when I look back at, well perhaps at my work at MIT, I still have my notebook from there; I had the impression they were too cursory. At the Bureau, I came down to the Bureau and I inherited an old cubbyhole of an office that had belonged to Brickwedde when he was running the low-temperature section. He left all his old junk there including some of his old notebooks and I picked out one of these notebooks and it was written in this rather discursive style which told me, it was very nice; it recounted in some detail exactly what happened. The other thing was we had another visitor at the Bureau there Bernard Kurrelmeyer from Brooklyn College, who had originally done some work at Leiden and wanted to get back in low-temperature research. So he came down during the summertime and was doing specific heat work, and he was keeping a notebook and I remember Russell Scott our section chief there remarking what a beautiful notebook Kurrelmeyer kept. You really knew what happened on any particular day. And it was really important, because thereís always a glitch that would happen. Maybe the power would go off or something that didnít seem significant at that time. When you go back later, itís very useful to do that. And itís a style which I havenít always followed since, unfortunately, but whenever I think of I try because many times over the years I would necessarily go back and search out old records and try to figure out what on earth I was thinking about.

Baym:

The other reason it might come to mind was whether you were aware that it was a very important experiment and you were trying to stake out priority.

Maxwell:

Well, as a matter of fact, no. I felt rather self-conscious and somewhat apologetic about the experiment on one level. You see because Shoenberg characterized it as a freak experiment —

Baym:

Yes.

Maxwell:

— and I tended to regard it that way. The other thing is, I remember when we told Condon about this experiment and he said, well he sort of laughed and he said to me, ďwell go ahead and do it I donít think youíll see anything. But do it anyhow.Ē He said, ďJust between us chickens I donít think youíll see anything. But go ahead and do it anyhow; if you do youíll get your name in all the books.Ē (Laughter)

Baym:

FrŲhlich, in a recent article, I think in the late Ď70s, said that you were not officially permitted to do the experiments and had to do them at night.

Maxwell:

Thatís not true. No, thatís not true. I donít know where he found that idea. He may have gotten that from a remark that Condon made at some banquet at some time when we were talking about this and he jocularly said, ďIíd like to tell you what my contribution was in a negative way,Ē and he recounted a remark heíd made. No, as a matter of fact, this I have to say about all of those people over at the Bureau, Russell Scott who was our section chief immediately over me, well he was a very conservative person. And Condon, even though they didnít think that there was probably any great chance of seeing anything, there was no attempt to discourage me. As a matter of fact, I appreciated that very much. We had a lot of freedom to do what we wanted to. There was no need to do it at night, although we did do it night, because in those days weíd work forever until the helium ran out. BAYM: Hereís a complicated question. By March 1949 you seem to have been close to getting results, from your letter to Slater on the 28th of March. [Maxwell to Slater, 28 March 1949. Copy in Urbana.]

Maxwell:

I had no results then. In March 1949 I was probably working on this AC method and I thought I was going to get around doing it.

Baym:

You say in this, he invited you to give a talk, and you say that the experiments are in an advanced stage of preparation.

Maxwell:

Well, I forget. Maybe I was then fooling around with the capillaries.

Baym:

Did you actually speak on mercury?

Maxwell:

No, no, we hadnít done the experiment yet. I hadnít done it; I was not going to say anything about it. Besides which, as I say, I felt in advance of having any result, I found myself self-conscious about it. Although it was rather interesting if I had had the result that I accomplished, Bardeen was at that conference, and Bardeen Iím sure would have jumped at it.

Baym:

When he heard about the effect from Serin it took him about five days.

Maxwell:

Exactly, I know that. If he had heard about it a year before, he would have taken off. I think there were only two people who were tuned in properly at that point to understand the significance of our work.

Baym:

Bardeen and Fröhlich?

Maxwell:

Bardeen and Fröhlich, yes.

Baym:

Can we back up to the isotopes themselves? What was the reason for growing the isotopes in the first place?

Maxwell:

These were things that were produced at Los Alamos I believe during the program there, and it was a product of neutron bombardment of gold, for whatever reason I donít know. I think the reason for using the isotopes in the first place, the reason why the Bureau got onto it, was they were using them for spectroscopic standards. And letís see, why mercury-198? I think itís probably about as pure an isotope as they could get. And so the isotope broadening and the spectra line would be minimized.

Baym:

Why did you choose mercury?

Maxwell:

Why did I choose it? Because it was there. As a matter of fact, I didnít know at that time you could get, that separated isotopes were available from the AEC. Thatís where the Rutgers people got it. If I had known that, I would have gotten after them, and probably would have done the experiment a little bit sooner because with three or four different samples you had more confidence; with just one sample as compared with natural mercury you had to be very careful. Thatís one reason why we, I diluted, added some gold impurity to natural mercury to see whether that would have an effect, because I feared, supposing we did see a very small effect, and people could say thatís because of the impurities.

Baym:

So your original idea of capillary change, then, is to an inductive —

Maxwell:

Yes, using resistance to an inductive technique.

Baym:

Could you summarize the crucial events in the year between March 1949 and 1950?

Maxwell:

Well, during that time I was diverted into another experiment it was a meeting of June Ď49 probably — maybe it was June 1948, Iím not sure, Iíll have to work these things out. There was a meeting in Washington of the Physical Society and a concomitant meeting of the National Academy. There was a paper there given by Houston (?) and Squire at Rice (?) (? 151). Squire had a lot of low temperature work started there, in which they did their first superconductivity experiment again in their Collins cryostat. And it really was a rather peculiar thing, it was sort of a Faraday — why they did it I donít know — but it was a Faraday induction generator. They had a tin sphere and a magnetic field and measured the Faraday — induced emf. And they got a result which seemed to contradict the Meissner effect. And Condon was at this session and got all fired up about this particular experiment. And there was some question about the whole thing, and he became interested in low temperature work. And so he collared me and suggested that we do some, suggested a simple experiment, you know see how each sphere is behaving in a magnetic field. And he suggested we just get a superconducting sphere and measure its period of oscillation in various fields and temperatures. So we did that experiment which is recorded there. [E. U. Condon and E. Maxwell, Phys. Rev. 76 (1949), 578.]

Baym:

This is the experiment with Condon.

Maxwell:

Yes. Immediately we got a curve and it seemed to have a break in it, and Condon jumped on this. Well, it looked like something. Well, as it turned out later itís an artifact due to poor technique. You see when I say that I was very sensitive to technique; this is one of the reasons. This was due to; as a matter of fact there is combination probably of two things. One of them is a small departure from sphericity in these spheres it has an anisotropy, a geometric anisotropy, and the other was that it was probably impure enough so there was a certain amount of frozen-in moment. So we had a combination of an induced moment and a fixed moment which very easily will give you something — which would give you sort of quadratic behavior in a field. I did some later, and then after getting this result it was questioned, and I remember sometime later Shoenberg explained to me what the problem was. I tried to refine the experiment by doing it with mercury which would be purer, and I worked with ellipsoidal bodies of mercury which I would freeze in a flask and then developed techniques for separating out these various effects. First of all, I knew there would be no frozen-in moment because these were pure materials, I was careful. And the shape effects acting I could eliminate by doing this thing in enough orientations so that when I average them the geometric anisotropy would average out. What I found with this particular experiment was that there was nothing there. I probably should have published a note to clean up this piece of confusion in the literature, — (laughter) but I never did. That took quite a bit of time actually.

Baym:

So this paper is later on.

Maxwell:

That was a note after the discovery in publishing this. (? 200)

Baym:

I have just one question, you mentioned Brockhouse up here. [Copy of internal memo, E. U. Condon, E. Maxwell, circa April 1950.]

Maxwell:

Yes. Well you see right after the first thing was published there were various speculations about what the possible cause was, you know (204) and it took a little while to get clued in on this. And there was a note from Brockhouse — Brockhouse actually had a note which he never published — I may be responsible for discouraging him, in which he made a correlation between essentially the lattice vibrations and the temperature shift. But by this time, Serin and Reynolds had already pointed out the possible correlation of the Debye temperature and the transition temperature and what Brockhouse did was probably the same sort of thing in different language. Somehow Iíve lost the documentation I used to have. He would have published it probably and he never did.

Baym:

Thereís this very early paper by de Launay and Dolecek from 1947. [Phys. Rev. 72 (1947), 141-143.]

Maxwell:

Debye characteristics. I probably had seen this, yes.

Baym:

The question is whether you remember this as important.

Maxwell:

I probably remember it, but I donít believe I connected it with anything.

Baym:

I see. Serin apparently did. According to Mike Garfunkel, he saw this very steep rise here.

Maxwell:

I donít think so. Iíll tell you why. No, I think Serin had felt — let me try to recollect the way these things worked out. You see I had no contact with Serin before the experiment, although I probably knew him cursorily. And while I was doing these isotope measurements I remember Iíd begun to get these results. Well, let me answer your question directly without being too roundabout. You see we both reported these results at the ONR meeting at Georgia Tech and what happened was I had gotten these results and I sent in a preprint. In fact, I circulated this; they asked that we circulate our abstracts to all the people at the conference. Well I circulated this to them, and then of course one came out, and it was very funny, on the program. I still have this copy; you see Iím listed on the program.

Baym:

Oh, marvelous.

Maxwell:

Then there was a sort of post-deadline thing produced. They came forward with this thing. Thatís superconductivity under stable isotopes. Well later we got together, and I remember Serin saying to me, ďGeez, our wives are awfully mad at you.Ē You see they had these isotopes on the shelf too, and I think they felt the same diffidence about this experiment, because the thing they report there is something else; thereís some work on impurities. And he said, ďBoy, our wives are sore, we stayed up all night checking things out.Ē And I suppose if I had been as sharp as some people I would have published my results immediately but I didnít. There were enough questions about whether or not these were really bona fide. I never regretted the fact that I didnít score a coup by a week or whatever it was, because essentially I think we supported each other very effectively at something that might not have been well received. Iím sure if they had independently earlier published, done this work and published it on the number of isotopes they had, there would have been no question. But the point is, now getting back to the Debye temperature thing, I recall that we were, I remember at the conference at the dinner we had there.

Baym:

This is the ONR meeting?

Maxwell:

Yes, the ONR meeting, we sort of got together and were trying to understand it. I think Serin, as I remember, might have said ďI think you know there may be something with the Debye temperatureĒ or something like that. But it wasnít very clear and he hadnít made any correlation. About a week later, they took their data and put it together and established the 1/2 power correlation [Tc M Ĺ], of course I only had two pieces of data of my own. Herzfeld was interested in seeing what possible correlations one could make and so we sat down and he took all the data and put it together, which was it turned out not a smart idea because our temperature scales were not necessarily coincident. (Laughter) If you did this there was some other power law, 3/8 or something. But of course as it turns out the 1/2 power is not inviolable anyhow as work much later showed. But it does seem to be the case for mercury, at least. So thatís how that came about, but I can say though that none of us really were terribly penetrating in our earliest analysis. At this ONR meeting, that was a meeting attended by Fritz London and Van Vleck was there. I remember them I donít remember who else was there. Letís see whether there is a list of attendees here. All the people whom you might think would certainly — I must have the papers, we donít have a list of attendees. And then I recall in trying to find some rationale for this, it was being discussed pretty widely and the first I heard of the Fröhlich theory was when Tisza called me up a couple months later and he was very much excited about it. He told me about the Fröhlich theory.

Baym:

Was this before the article actually appeared?

Maxwell:

No, this was after. The article appeared in March, and his letter to me is sometime in... [July 20, 1950]

Baym:

Fröhlichís appeared quite late.

Maxwell:

Fröhlichís appeared late, but it actually had been submitted earlier. That is, Fröhlichís paper I think was in press before our results appeared. His final paper was in press, but when he got out our results he did have a letter printed I think to the Physical Society. [Proc. Phys. Soc. Lond. A63 (1950), 778. Appeared July 1, 1950.]

Baym:

Itís here, yes.

Maxwell:

Yes, thatís right. That was his longer paper I think was already in press.

Baym:

The long paper was received May 16th.

Maxwell:

That was after we reported. But of course he had been writing it for some time. It was —

Baym:

While weíre on the subject of the Tisza letter [Maxwell to Tisza, July 6, 1950], one thing that came up there was the atomic volume effect. Could you explain that?

Maxwell:

Iím trying to remember how this came about. Oh yes, there is a pressure shift in the transition temperature of superconductors, so that one of the thoughts that occurred to me — I donít remember whether anyone else suggested it — was I thought well perhaps we know thereís a shift in volume with isotope number maybe we can correlate the isotope shift with the volume shift and correlate this with the pressure shift. Well, it turned out that the effect is only 1/4 as big as required to give it the required proper effect, and as a matter of fact I retained three papers of what was going to be our letter to the editor at some point, which I never wrote because it was just too nebulous an idea.

Baym:

You sent a copy of that. [Three pages, dated 6/19/50 — typewritten.]

Maxwell:

Yes, I think there were four sheets to it or five. One of the things that struck me was that the pressure shift for superconductors is positive for all superconductors, except in thallium where it was negative. And so it occurred to me well maybe we should look at the isotope of thallium, and it got me going on that, and well as it turned out the sign of the isotope shift in thallium is the same as in all the other superconductors. It was just a blind alley.

Baym:

Thereís some Russian work here.

Maxwell:

On the atomic volume, on the pressure dependence problem. I think that was probably talking about atomic volume. I think it was Lazarev and Sudovstov who had measured the pressure dependence of a temperature.

Baym:

The results the Russians found for thallium —

Maxwell:

— increase the temperature.

Baym:

Yes.

Maxwell:

Thatís right, and I wasted a lot of time with thallium (laughs). This is a sort of secondary thing, but I ran into another effect which it took me a long time to understand and unscramble. That was super cooling, super cooling with transition and I had such pure samples then I was doing tremendous super cooling and not getting real transition temperatures and it took me months before I straightened that problem out.

Baym:

When did you become aware that the results indicated the role of the electron-phonon interaction?

Maxwell:

Actually about the time that I became aware of FrŲhlichís and Bardeenís work, it was really their analysis that made me accept the thing as a reasonable explanation.

Baym:

So it was not something in the air.

Maxwell:

It was not something that was in the air. You see, as a matter of fact, we looked upon a superconductor as something in which the electrons suddenly became free of the lattice at the transition temperature. And while on the other hand, in that experiment on the sphere which I say was an artifact, we do talk about lattice interaction, it was a sort of vague idea. I mean clearly if there was an effect there it was a lattice interaction. But I think beyond saying that, I donít think, I mean I know we didnít have any clear idea of just what the mechanism might be.

Baym:

Were you aware of the intentions of doing such an experiment by Bob Webber at the Naval Research Lab?

Maxwell:

No.

Baym:

And also de Launay was also thinking about the problem at the Naval Research Laboratory.

Maxwell:

No, we never discussed that. As a matter of fact, I knew only of the Serin intention because while I doing my experiments, and when I got my first results, I hadnít announced them yet, I had a visit from Immanuel Estermann, who was then at Carnegie Tech. And he used to spend summers at the Bureau and he came down and I told him about —

Baym:

Heís a molecular beam man.

Maxwell:

Yes, Estermann and Stern. And he, I showed him these results and said there seems to be an effect and he said ďwell, you know, I think people at Rutgers were thinking about doing this but I donít think they have gotten anywhere.Ē And this was a couple months before. So when they got onto the idea I donít know, but I suspect — well I donít know you may have some information on them — but I suspect it was not very very early.

Baym:

A general question of when you became aware that the Serin group was working on this problem. They had submitted a proposal to the AEC to get isotopes.

Maxwell:

I didnít know that.

Baym:

You had not seen that at all.

Maxwell:

All I knew about it was probably a month or two before that March of that winter I heard Estermann told me about this and I didnít, it was one of these vague rumors that one didnít —

Baym:

After that time had you communicated with them, apart from the ONR meeting?

Maxwell:

Well, prior to the ONR meeting, no.

Baym:

Because you both refer to each otherís work in there.

Maxwell:

Well, I think we agreed, you see at the ONR meeting we agreed to submit letters at the same time.

Baym:

So that was at the ONR meeting.

Maxwell:

As a matter of fact I really didnít know them very well. I probably had only a nodding acquaintance with Serin at that time. I didnít know any of the others. So thatís how we really got together.

Baym:

Were there any significant differences in the technique, yours and Serinís?

Maxwell:

Well, I donít know about significant, but I can tell you what they were.

Baym:

Yes?

Maxwell:

My technique was woefully simple. I donít have the original apparatus, but I have the second one I used. I tried, I thought about these various effects, capillary, resistance of the capillary, thereís audio-frequency technique and then I decided to go ahead and do something with what was around. So I did a simple DC experiment. We used to do a lot of work in the Bureau where off in the attic they had a museum of old apparatus you could collect parts from (laughter). In particular there were a lot of copper glass seals there. I think these originated from the days when probably they were learning how to do glass blowing, you know, practicing glass blowing. In those days everything was pretty informal in the Bureau; I could walk in to the glass blowers and say ďlook will you do this or this.Ē While I stood there he would go ahead and do it. And so I found this nice piece of glass tubing with a copper seal on the end. Went down to the glass blower and I said, ďWill you neck this thing down like this?Ē And he did, so I wound the coil on this, in a lathe-on this piece of glass, and then very quickly — Iím pretty sure I made this apparatus with my own hands — made a cap and soldered the thing into a cap and the whole thing went onto a helium Dewer. And the idea was that this was a pick-up coil and I simply sealed off the mercury in a capillary and inserted it here and put a cork on the bottom and then this whole thing we had borrowed some Helmholtz coils which Arthur... (? 020) had there and put them around like this. At the Bureau there we had a central steady DC supply; it was a big storage battery pack that was connected right on the various laboratories. So I just connect up to this in series with a rheostat and this thing went to a galvanometer with a shunt and all I did was to start in at a given temperature, slowly raise the field until I saw a kick in the galvanometer. That was the experiment.

Baym:

What generally was the role of Scott and also Herzfeld and Condon?

Maxwell:

Well, they were sort of advisory in a sense they were cheerleaders on the side. Herzfeldís role really was in first of all initial information he brought back from Zurich, or wherever it was, which gave a certain respectability to the experiment as far as that is concerned. And he participated in some of the earlier discussions as to how to do the experiment, and he was the leading mind behind that attempted correlation that we made. He liked to be kept informed of what was going on, but he wasnít very active in it. Scott was again simply supporting in a general cheerleading supportive role, making it possible to do these things. Scott was the section chief. Incidentally it was the liquefier which Scott and Klick (?) had built, in which we were doing all the work. And they built a Simon — we did these experiments in those days with a Simon expansion liquefier, which to make liquid helium — it was a wonderful device. On Friday, they would liquefy hydrogen. We had a hydrogen liquefier there, and then you would use the hydrogen to precool the helium down to about 100, and then expand it under pressure, and the beautiful thing was that we would get something like 330 cc of liquid helium delivered into the Dewer. There was no precooling because the column gases would do all your precooling; it was really a very beautiful technique. We made that last for 18-24 hours. Itís amazing how we managed to work. Scott was in charge of the laboratory, and he really made possible the various logistics that we took advantage of. This experiment was just as simple as this: a pick-up coil with a sample inside, a means of slowly raising the field and looking at the transition on the galvanometer. What Serinís people did was they used an audio, an AC technique, I think. As a matter of fact, they had reported some work earlier on experiments at audio frequencies on superconductors, although it was actually published later. But this is what they were working on in 1949, rectification phenomena.

Baym:

This is a technical report March 15th, 1949 to the ONR.

Maxwell:

This is something that Serin sent me many years later when I was interested in this phenomenon. But they used an audio frequency technique; they would superimpose a slight AC tickling field on a DC field and look for a change in AC signal. That was all that was involved. So that was that.

Baym:

The ONR raises one question. Do you think it was in any way a help to either yourself or Serinís group to have been supported by ONR?

Maxwell:

Oh, it was a tremendous help. You see, as a matter of fact, the support of basic research right after the war was largely due to ONR.

Baym:

I donít mean in dollars, but do you think for example it made it easier for you to have access to isotopes.

Maxwell:

Not in my case. Logistically, that was really of no consideration.

Baym:

Letís turn now to Mendelssohn. You sent a letter to Mendelssohn — [Maxwell to Mendelssohn, April 12, 1950.]

Maxwell:

Well after we got these results —

Baym:

Why Mendelssohn particularly, rather than Pippard?

Maxwell:

Well you see in 1949 there was a low temperature conference, and all the people in low temperature in Europe went up to MIT. I and John Tolman and Russell Scott and Condon, who had become interested, got to meet some people in low temperature physics. Mendelssohn and Shoenberg seemed to be the honchos of superconductivity. Pippard evidently was the up-and-coming bright young man but he wasnít yet the leading figure in terms of position. And anyhow Shoenberg and Mendelssohn were essentially the group leaders in this area in superconductivity. And besides if I wrote to Shoenberg it was equivalent to writing to Pippard and so there was no distinction as far as I was concerned. You see Mendelssohnís reply to me when I first told him about these results is very interesting.

Baym:

We have the reply but not the letter you sent.

Maxwell:

Oh, you donít?

Baym:

Do you have a copy of the letter?

Maxwell:

I must have. Let me see if I can find it. (Searches through drawer.) This is Gorter, Ď52, this is Pippard, and this is probably right after the Oxford Conference. He says, ďI enclose Ginzburg and Landau in what I hope is an accurate translation. Iím not yet sure whether I believe it.Ē

Baym:

Thatís very Pippard, yes. (Laughter) This must be from Bardeen?

Maxwell:

No, from Paul Marcus. Hereís a letter to Taconis.

Baym:

In Dutch?

Maxwell:

Well, thatís a joke between us. (Laughter). Dirk Declerk (? 118) had spent a year at the Bureau and I had a question to ask Taconis and would it be a good idea if I wrote to him in Dutch? And Declerk wrote it in Dutch. And so Taconis wrote back in English. This was written by Ernie Lynton who was in Leiden at the time. (Laughter) Gorter, Ď51. It must be in the other file. (Searches through file.) I wrote to him and to Shoenberg at the same time. That was actually at Condonís suggestion. Letís see, this is my letter to Slater. This is a letter to Tisza. Well, anyhow all this is strictures about frozen-in moments and sponges and so forth. We were very much aware of these things, and we were very much sensitized by the need not to make a goof like some I had made on one occasion and then of course there was this case this horrible example of Ogg, and one of the things that I had learned very early was to make startling discoveries which are wrong.

Baym:

To turn back to the ONR meeting for a moment. Were people aware of the implications of your work?

Maxwell:

They were sort of open now. London didnít put it together, and Van Vleck certainly didnít say anything if it occurred to him and I think you see it was not the direction in which people were thinking. It all seems very pat today, but it really wasnít in those days.

Baym:

Let me ask a similar question about the Washington meeting. You sent a post-deadline paper there.

Maxwell:

By that time Bardeen and Fröhlich were aware of this.

Baym:

Was the Serin group at that meeting?

Maxwell:

Yes.

Baym:

What about further work you did on tin?

Maxwell:

Well the further work on tin, oh, you see one thing I became aware of was that there were tin isotopes. In fact I became aware of the fact that there were stable isotopes you could get for the asking. And so we immediately did get samples of some tin and thallium and these were in compound form and I had to enlist the assistance of one of the chemists in the Bureau to reduce these to metal. It took some time and so the idea was to look at everything. Of course by that time I guess Lock, Pippard and Shoenberg had done the first work on tin after, that is, after we told them about mercury they got onto the tin work. They got some isotopes from Harwell and you see there I forget when theirs was published.

Baym:

Mendelssohn sent you a letter on December 2nd, 1950 telling you about their experiments on tin.

Maxwell:

Yes, well that was about the time — you see what happened was that both Cambridge and Oxford got samples from Harwell.

Baym:

Yes.

Maxwell:

And so, Harwell people got their name on both papers. And Mendelssohn decided to look at tin isotopes by a resistance technique. And the Cambridge people decided to use the inductive technique because, well they already had a lot of experience in that area and besides Lock had an apparatus in which he was studying something else which was beautifully suited to this thing and so they immediately worked up a very good experiment.

Baym:

Was Mendelssohnís letter to you the first that you learned about the British experiments?

Maxwell:

Well, I heard from Shoenberg also, but Iím not sure which was which. I heard about them both at more or less the same time. Letís see I had one from the 20th of November from Shoenberg in which he says ďmany thanks for your letter of November 13rd.Ē That was much later. They originally got tin isotopes from Harwell. Did I send you a copy?

Baym:

No.

Maxwell:

Well, I may have a copy here. Letís see, I donít recall whether my report on tin-124 was before or after — letís see, is that a copy of that paper?

Baym:

Yes.

Maxwell:

Hereís a copy of Shoenbergís letter.

Baym:

May I take this?

Maxwell:

Sure.

Baym:

Thank you.

Maxwell:

As a matter of fact, I already had tin-124 by July so that well before the tin work I was then struggling to get a technician assistant but bureaucratically I couldnít get it.

Baym:

FrŲhlich, in his account of the history, mentions a lab in England that missed the experiment because they refused an offer of isotopes.

Maxwell:

That could well be, I donít know which it was.

Baym:

The question is which.

Maxwell:

No, I hadnít heard that story.

Baym:

Can you think of any other labs where it might have been natural to do these experiments?

Maxwell:

I would think Los Alamos was probably farther ahead in its low temperature program and it would have been a natural place to do it.

Baym:

Thatís right.

Maxwell:

But I think at Yale, I remember Lane sort of grousing because he just missed out on it at Yale. And I think he had Berlincourt do some isotope experiments on other property.

Baym:

This is Ted Berlincourt?

Maxwell:

Ted Berlincourt, yes. I seem to remember that. But, well you know itís like all of these things, ďWell, I almost did it.Ē So you see when I did my first experiment I measured the 198 and the natural mercury in separate experiments. Now it was suggested maybe it would be smart to put them together and look at the difference. But in the first place, I didnít know if there was a difference, whether it would be large enough to resolve, and the other thing was that I was so skittish about this valuable mercury-198. I had these visions of the thing breaking in the apparatus and getting mixed up with the other stuff, so I had to keep everything separate. That apparatus was broken, unfortunately, but I have the one in which I did the tin and thallium work. There was a closet in which it was preserved and they later set it up for me after I left the Bureau.

Baym:

Itís beautiful.

Maxwell:

Iím very proud of this apparatus. I wound these coils myself on a lathe and they contain something like 40 or 39,000 turns of #44 wire.

Baym:

Very good.

Maxwell:

Some years later when Karl Shifton was trying to clean out some of the Bureau he asked if I wanted some of this stuff and I let him send it on. The old apparatus I probably threw out. The glass broke, and it was useless, so that was the end of that. Incidentally, this is apropos of another subject. If youíre researching the history of superconductivity, I would like to point out probably the first validation of the Ginzburg-Landau theory was done at the Bureau by Olan Lutes who was an assistant really a student of mine. You see sometime I left the Bureau in 1953, but sometime before that about 1951 or 1952, he came to work as an assistant for me, and he was getting his degree at the University of Maryland at the same time. And the problem we started to work on was superconductivity of tin whiskers. We developed a technique for growing tin whiskers, something we found in the literature. And he worked out a very nice technique for measuring the resistance transitions. And I gave him, I remember, the copy of the translation of the Ginzburg and Landau article that Pippard refers to. Frankly I never had the stomach really to sort of dig into it myself. My reaction probably was the same as Pippard; it just looked a little bit too contrived. But Owen worked at it, and he got some very nice results, I remember the first initial, very sharp transitions we got on these things. And then he did some rather detailed work and he did his thesis on it. And the results were published in the Physical Review but he was able to explain the sharpness of the transition of temperature dependence in terms of the order parameters rather the surface energy parameter of the Ginzburg-Landau theory.

Baym:

Thatís very good.

Maxwell:

And that was probably about 1955. [0. S. Lutes and E. Maxwell, Phys. Rev. 97 (1955), 1718; see also E. Maxwell and 0. S. Lutes, Phys. Rev. 95 (1954), 333.] Thereís another thing I might direct you to as far as type II superconductors. Of course we had type II superconductors all around us in those days. We didnít know it and we thought they were poison.

Baym:

Yes, yes.

Maxwell:

Thereís a paper published in the Physical Review around 1951 I think by Love, who was then either at the University of Pennsylvania or maybe he moved on to the University of Colorado at Boulder, in which he makes a measurement on tin-lead alloys and measured their magnetic moment as a function of magnetic field and he sees all the standard type II superconductivity behavior and he distinguishes two critical fields which he calls Hc1 and Hc2.

Baym:

Really?

Maxwell:

Yes.

Baym:

Remarkable.

Maxwell:

And nobodyís ever paid any attention to that. As a matter of fact, I particularly noted that because the thing that I was thinking of, one of the things I was planning to do after some of that isotope work was to investigate solid solution superconducting alloys. Well, I had a critical field technique and it might be interesting to see how things behave as a function of dilution. I probably would have run into that, but I was rather amused I noted Loveís article long before I was aware of type II superconductivity as a thing in itself. What amused me were years later that he had really anticipated this. Youíll find it I think sometime probably Ď51 or Ď52 in the Physical Review. [W. F. Love, E. Callen, and F. C. Nix, Phys. Rev. 87 (1952), 844; W. F. Love, Phys. Rev. 92 (1953), 238.] And itís really beautiful. He simply doesnít identify it in terms of what the underlying phenomenon is, but itís also very interesting that right after his initial work on the isotope shift and the lattice, electron-phonon interaction, Bardeen felt there was sort of a lull, things just didnít seem to work beyond the initial idea. And he did a lot of work on the problem of surface energy that is the special surface energy between the intermediate state superconductors. And I donít think he ever talks about negative surface energy.

Baym:

Bardeen?

Maxwell:

Bardeen. In fact, itís his article in the Handbuch der Physik; he goes on at length about this. I think so; maybe Iím wrong. ďThe energy of the boundary between normal and superconducting phases.Ē Well, he talks about Ginzburg-Landau; he doesnít talk about negative surface energy.

Baym:

What year is this?

Maxwell:

This is about Ď56. Its post-Bardeen and FrŲhlich but its pre-BCS. Yes... were you successful in talking to anybody who was contemporaneous with Serin and remembers, Mike Garfunkel, for example?

Baym:

Lillian did talk to Garfunkel, yes.

Maxwell:

And heís the only one whom I could think of.

Baym:

Nesbitt was a technician.

Maxwell:

Nesbitt was a technician, and Wright was a graduate student. There are other contemporaries. Peter Weiss was on the faculty then. Torrey was there, whatever they may remember, of him. These things get lost very easily.

Baym:

Thank you very much. It was really a pleasure. Finally, could I ask you to comment more generally on your impressions of how the war affected later solid state research?

Maxwell:

The war gave us a lot of tools to work with, as technology was developed during the war. But more than that, not the war itself but the aftereffects created an atmosphere for scientific research which simply had been unmatched to an extent. That is, it was a time in which the ONR, I think, played a very decisive role in encouraging research and funding research and making money available. It was very effective; they had a very good crew there at the ONR. People like Emmanuel Piori were there, Immanuel Estermann was there for a time, Lawson McKenzie, and you name it, there were all kinds of very competent people who spent some time there who made the money available.

Baym:

The war seems to be a sort of a counter-example to the flow from basic to apply. What was coming out of the war was applied research which enabled tremendous advances in basic research after the war.

Maxwell:

I think one of the reasons is all these tools became available and money was available. The thing of the war again was to demonstrate that science could really deliver something. In fact it demonstrated it so much that is was terribly oversold in later years, but we emerged from the war with these wonderful, gee-whiz developments: atomic energy, the atomic bomb, the radar that could do all these things. And people had the idea that the possibilities are limitless. Of course the amount of money involved was really relatively small by later standards, but it was enough. It was very generous funding for people who before the war had nothing at all to work on. I mean, it was a big difference, a big jump from zero to one, if you like. And the other thing is that for example the research laboratory in electronics here inherited a good part of the equipment of the Radiation Laboratory and it was a tremendous help. As a matter of fact, a lot of it was also distributed to other universities and there was so much of it, so it did make a lot of equipment immediately available that it would have taken a long time to acquire otherwise and also people who had techniques which they could then go and use.

Baym:

I think also the hastening of the techniques — if a person decided I need microwaves, for one person to develop it would have been impossible.

Maxwell:

What the war demonstrated was that you could really put on the steam and develop things very very rapidly. Thatís why it was so amazing. It also created a body of people who had acquired a certain amount of technology and also a certain philosophy or psychology which helped an awful lot. So it certainly had a positive effect on that score. And you also assembled a rather large body of people who had become skilled and trained in a certain area and who were then sort of turned loose on universities and on industry. I remember very clearly — this is maybe apart from the point: at the time the Radiation Laboratory was closing down, it immediately became a mecca for industry, universities, for everybody to come and hire people. Having remembered the lean days of prewar, this was a phenomenon I never expected to see: employers waiting in line to talk to people, people having three or four, as many offers as you really had the interest to get. I remember the Naval Research Laboratory had a rather unique program on; they were interested in picking up people, so they ran some planes up from Washington. They were having regular excursions; you just sign up.