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Oral History Transcript — Dr. Fritz Reiche

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Interview with Dr. Fritz Reiche
By Thomas S. Kuhn and George E. Uhlenbeck At the Rockefeller Institute, New York, NY
April 4, 1962

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Fritz Reiche; April 4, 1962

ABSTRACT: This interview was conducted as part of the Archives for the History of Quantum Physics project, which includes tapes and transcripts of oral history interviews conducted with ca. 100 atomic and quantum physicists. Subjects discuss their family backgrounds, how they became interested in physics, their educations, people who influenced them, their careers including social influences on the conditions of research, and the state of atomic, nuclear, and quantum physics during the period in which they worked. Discussions of scientific matters relate to work that was done between approximately 1900 and 1930, with an emphasis on the discovery and interpretations of quantum mechanics in the 1920s. Also prominently mentioned are: Niels Henrik David Bohr, Ludwig Edward Boltzmann, Max Born, Louis de Broglie, Byk, Compton, Albert Einstein, Arnold Eucken, Werner Heisenberg, Joe Keller, Hendrik Anthony Kramers, Krigar-Menzel, Werner Kuhn, Rudolf Walther Ladenburg, Alfred Landé, Stanislaus Loria, Max Planck, Radernacher, Rotzsayn, Clemens Schaefer, Hermann Amandus Schwarz, Otto Stern; Bad-Neuheim Conference, Naturforschertag (Salzburg, ca. 1909), Universitaet Berlin, Universitaet Breslau, and Universitaet Goettingen.

Transcript

Session I | Session II | Session III

Kuhn:

I remember last time particularly you told us something about Planck' s lectures in physics, and also something about your training in mathematics. I wonder who else you took physics with?

Reiche:

I took experimental physics already in my first two semesters in Munich. I attended lectures by Roentgen. Later I repeated the same one year course in experimental physics, attending lectures by Paul Drude, who was very very good - not only a good physicist, but also a good lecturer, a good speaker.

Kuhn:

Was the ground covered in Munich approximately the same as the ground covered in Berlin?

Reiche:

Approximately the same, however, it was later. I cannot remember whether there was an essential difference, but I think it was approximately the same things. This was a big experimental lecture, It is very rare here, or usually even not given. For instance at the Heights and NYU they had an experimental lecture, but it was more naive and not as extended as these big experimental lectures in Germany. There were demonstrations. A lot of demonstrations. A man like Otto Lummer in Breslau was a very famous lecturer, especially in demonstrations.

Uhlenbeck:

Like Pohl in Goettingen later?

Reiche:

Like Pohl, yes.

Uhlenbeck:

Did you have to do some experiments yourself?

Reiche:

Yes. After my Ph.D. Eugene Goldstein was, I think, Privatdozent at the University. He was already an old man. He was the discoverer of the canal rays, which played at that time a pretty big role, but he was an especially modest man, so that he never was very famous. He came to all the meetings, but he couldn' t make something out of himself. He was well-known to me and he knew me. Planck and he decided that Reiche must be sent to some experimental place, or he will become too theoretical.

Therefore, they decided that I should go to Lummer in Breslau. So they sent me to Breslau, and there I tried to learn a little experimental physics. I did really quite a little, but it was terribly difficult for me - much more difficult than the whole of theoretical physics, I would say. Always something was missing, and I had bad luck in breaking things and making explosions. At the same time, by the way, Max Born was at the same institute in Breslau He worked, although not together with me, but on another problem. He completely agreed with me that this is a terrible thing, to have the correct wooden blocks — it was a little too low or it was a little too high, but you couldn' t find, the right piece of wood to place between to give the correct height.

So a lot of things happened then. I made big floods, inundations, so thatall the observation books were running around in the room. So I learned how difficult it is to make good experiments. First I think I worked under the guidance of Ladenburg, Rudy Ladenburg. It was something about intensity of X-rays. I think he was connected with some hospital at that time. I helped him a little. I do not know whether there really came out of this a useful procedure. Then, later, Lummer asked me to repeat things in which he was obviously interested, and I became interested too. It was that well-known phase anomaly if a convergent beam goes through a focus, or a caustic generally.

It looks as if there is a jump of phase by pi over two or pi. This had experimentally been proven I think by Sagnac. It was derived first very briefly by Gouy, a famous wench physicist, and later on again by Sagnac. I think Sagnac had also made experiments. We repeated in a more modern way, this same thing, and found really that one can prove that it is not a jump, of course. It is a gradual phase change, but on a pretty short distance on both sides of the focus. So it is really that the convergent wave going over into a divergent has a phase difference of it if it is in three dimensions, as far as I remember, and it over two in two dimensions. I tried to prove this also.

I was not quite successful. I have the feeling now that what I did was much too complicated. Later, Debye did it much more elegantly and better. So he is usually quoted if there is some speaking about this phase anomaly. That was one thing.

Then, later, I was working together also with Lummner himself on the emission of what we called at that time a Bunsen plate.... Then we measured, I think, some infra-red radiation, because I remember that during this procedure we used a bolometer - I do not know whether it is still in use now. It's a very sensitive instrument, and one day I remember that something was wrong - I had the feeling.

Instead of being very careful I put my fingers in, and in the same moment the whole bolometer was of course destroyed The result of this thing was, or the aim was, to check the dependence of the radiation on the angle with the normal. I cannot quite remember what really came out. I think it depended on the depth of the plate. In some lectures of Helmholtz, I think, there was a very simple derivation of the dependence if Lambert's law is correct. That's what he checked. It was not very accurate, but it came out approximately like the Helmholtz formula really was. This was I think everything.

Uhlenbeck:

Parallel to such a course of Drude or Roentgen, was there not a laboratory course in which one did set up experiments?

Reiche:

Yes, there was, yes. There was what we called in Germany a "Praktikum."

Uhlenbeck:

And did you take that?

Reiche:

Yes. One had to take that. I think one had to take it.

Kuhn:

Would that be a fairly elementary course? Did you take it early in your college?

Reiche:

Yes. First simple, purely mechanical things. A few in heat, and an extensive second part in electricity - electric measurements. I must say I was terribly impractical, there is no doubt about it. I failed it always, and was not personally very enthusiastic about having to take it. At last I came through, and my numbers were not too far away from those who were marked with the correct numbers. It was not very agreeable. Who was at that time in Berlin then? I think the older, what you would call graduate assistants were directing and guiding this course. There was a man (Leithauser), who knew every circuit arrangement, and he showed me how to do it and gave a diagram. I followed him, but I had the feeling, "Why am I doing this?"

Kuhn:

Was this the only course in experimental technique that was required?

Reiche:

Yes, at least the only one which I took. This was of course an elementary course. The more advanced course was only taken as far as I know if you intended to make a Ph.D. thesis in experimental physics. Since I had already decided on my attraction by Planck to do my thesis on the theoretical side, I did not take this advanced Praktikum.

Kuhn:

Am I right then, in having the impression that the physics curriculum would have been Planck's series of lectures?

Reiche:

And also some side lectures, which I heard, I think, at approximately the same time. I cannot say exactly. There was a man who was not very famous. He was Krigar-Menzel. He was a nephew of a very famous German painter, Adolph Menzel, who was a famous man and is still, I think, in the old German history, especially the time of Friedrich the Second, or Friedrich the Great. Krigarnzel, who quite obviously was a pupil of Helmholtz, followed exactly the very well-known lectures on theoretical physics, published by Helmholtz, or later published after his death.

Uhlenbeck:

Was that a Privatdozent?

Reiche:

He was a Privatdozent as far as I know. Later usually the Privatdozent got the title of Professor. Well, they were not paid as professor, but they had the title of professor, but had not a real office or official duties.... There was still another man. I do not know exactly whether he was what you call extraordinarius - an extraordinary professor. Wehnelt was his name. He was at approximately the same time. I think he was also chairman in the Praktika, in the elementary as well as in the more advanced. But as far as I remember there was, at that time, only one professor of theoretical physics and one head of the experimental institute. Later, after Warburg died, I think Drude came, he was his successor, and after him Rubens.

Kuhn:

A man who went through to a Ph.D. would know how much of what sorts of subjects? How much mathematics, as a matter of course?

Reiche:

As I said last time, I was not well-advised in my preparation, especially not in mathematics. This is still worrying me. It was different in Göttingen as I heard later from Born. There you were trained very, very systematically. At that time we didn' t know anything about matrices. Only to mention one sale. I remember that once, I think it was in connection with a paper by Born, matrices were being used, and we didn't know this. We didn' t learn it. I cannot remember that anyone at that time really used it extensively as the mathematicians would. I attended lectures of different people. But as I told you already, I was, in part, quite frankly bored - not by mathematics, but by the way in which it was taught. The old Schottky was a relatively old man, and Frobenius was not a young man. Schur was not an old man but I didn' t understand him well enough.

Uhlenbeck:

But you did have to take some kind of examination in mathematics, didn't you?

Reiche:

Yes. It was only a short examination, so far as I remember. I took it with the old Hermann Amandus Schwarz. The use was that one made him a visit first, and then he asked which lectures one had attended, about which parts of mathematics one did not wish to be examined. So he examined me, I think it was only a quarter or half an hour - something like that. Orally. There were no other examinations, no written examinations like the Prelims here, Only the thesis.

Kuhn:

What were the examinations in physics?

Reiche:

I was examined by Planck in one hour or one hour and a half - I do not know exactly. This was very convenient. He lived in the suburbs of Berlin, in what's called Grunewald. I could go out to see him there, and take the other examination....

Kuhn:

So these oral examinations were the only exams you ever took?

Reiche:

Yes.

Kuhn:

How many subjects were you expected to be prepared in?

Reiche:

Theoretical physics, experimental physics - I was examined by Rubens at that time and two other side fields, mathematics and philosophy. Also in philosophy one visited with the professor. I asked him to examine me about Greek philosophy or something like that, so it was not very bad.

Kuhn:

On the theoretical physics examination, what subjects would you be expected to know?

Reiche:

Let me say that it would be approximately what is contained in Planck's published lectures. This goes certainly until the canonical equations. At the moment I am not quite sure whether he at that time, had already talked about the Hamilton Jacobi method and so on, but probably not.... It came up a little later in connection with quantum theory. Then he added it of course to his lectures and also to his book. The main things were mechanics, mechanics of [deformable] bodies, electricity and magnetism.

Kuhn:

Now would that be a good treatment of Maxwell's theory in electricity and magnetism?

Reiche:

Yes, I think so. A little different from what you do today, I think.....

Uhlenbeck:

Were the books already out at that time?

Reiche:

No, they were not. You did. it from your notes then.

Kuhn:

You must have used some books didn't you?

Reiche:

No, it was not obligatory, or even suggested, to use other books. Planck gave everything. Of course, I remember that I had the Kirchoff lectures which however are pretty much difficult for the beginner. The mechanics, especially, is very involved. I don' t think that I used it or could it extensively....

Kuhn:

What about Hertz? Was this much used by students?

Reiche:

I don' t think so, no. I had it too. Reading Hertz would mean reading papers. It was not a textbook, in this sense. Later on one could try to understand the mechanics, I can only say that I myself felt in this respect. The Hertz works were certainly a study for itself.

Kuhn:

The appearance of Planck' s lectures changed this in Germany?

Reiche:

Yes, changed this,...

Kuhn:

When you taught at Breslau what books did your students use?

Reiche:

They used Planck, and probably - I cannot tell exactly when this started - Schaefer's book. I am not quite sure when Schaefer's first volume came out, but it was approximately at the time I was at Breslau. It might be a little earlier.

Kuhn:

Any others that were standard?

Reiche:

Well, later Joos came out. Several people preferred this against Schaefer, because it was quite condensed and shorter. Planck obviously was not of this opinion. He was very enthusiastic about Schaefer's books and also corresponded about different special problems or special items with Schaefer,...

Uhlenbeck:

For instance, Boltzmann's Vorlesungen Ueber Gas-Theorie came out quite early.

Reiche:

That's right, yes. I read it, I remember that I read it, but I could not say when or whether it was during this first three years which I attended the lectures of Planck. I think it was later, probably, that I read it. I cannot remember whether Planck gave some aspects of kinetic theory of gases.

Uhlenbeck:

You don't remember whether he ever gave a reference to Boltzmann, in his lectures?

Reiche:

You know that he was not on good terms with Boltzmann? In the book of course he does. Whether he did it in his first Waermestrahlung lecture, I am not sure. I guess, yes. This I remember quite distinctly, he did write down the Boltzmann equation. I mean s= k log w. So I guess be mentioned the name of Boltzmann.

Uhlenbeck:

But not the book Vorlesungen Ueber Gas-Theorie

Reiche:

This I don't think so. When I came over I was astonished about the very extensive use of books in lectures, in elementary lectures and in advanced lectures....The question, "which book do you use?" This was a question which usually was not asked in Germany.

Uhlenbeck:

Everything was done by notes there?

Reiche:

By notes. This was, of course, not quite single. One had gradually to learn to attend, to hear and to write and to think a little, also. One had to see whether one really had correctly understood, because he talked, and he continued talking. I am pretty sure that I did it not very well, this hearing and writing. That was also the reason, which I mentioned already last time, that I took, for instance, calculus twice two semesters in Munich and later with Hermann Amandus Schwarz. He was very extensive and went into details, fine details, which I did not remember having heard in the Lindemann lectures.

Kuhn:

And even in the more or less elementary calculus, there were no standard books that you used with this?

Reiche:

Yes, there was a book, which was probably not a good book, by Kiepert. I remember this - differential and integral calculus. That, obviously, was recommended by Lindemann, because I had the book from the beginning. Two very, very thick things. Many curves were discussed in the applications. But on the whole, I think the basic things were pretty sloppy, from the more modern standpoint.... I told you last time that Planck gave problems. But, for instance, it was greeted with enormous enthusiasm when suddenly, not at the beginning of my studies but much later, the little book with problems on physics appeared. I don't remember the name of the author. Such a book did not exist.

I remember that I tried to find some book, and I came across, an interesting French book written by a priest or a monk. This was an excellent book in which problems were put down out of different fields of physics. I think also some suggestions how to solve these things, But in Germany such a book did not exist until 1910 or later.

Uhlenbeck:

Was it common to use books in other languages? What about Maxwell' s Treatise?

Reiche:

Oh yes, well of course thats what I read. This was, by the way, already translated. At least I know that I had Maxwell, but it might be a little later, not quite at the beginning. This, I guess, was mentioned by Planck. But also this was not I would say, a textbook. One sees how the thing originated and was developed, but not in the sense of a good text. The more or less good text books were really, first, the books by Helmholtz. Those, by Kirchoff, were too difficult. There is no doubt, it was too difficult even for third to eighth semesters. Mechanics, especially, was too difficult, but the others were a little better. But also the theory of molecules with the Boltzmann equation, and solutions, or trial solutions to the Boltzmann equation, was also too high, in my opinion, at that time.

Kuhn:

When you went to Planek's lectures in Berlin, how many people would there have been at those lectures?

Reiche:

I would say between 80 and 100, something like this.

Kuhn:

And how many of those people would go on in physics at all?

Reiche:

That is difficult to say. Probably many of them became high school teachers. This, by the way, was the same in my time in Breslau, which was twenty years later, from '21 to '33. At that time, also, I had very, very few Ph.D. candidates. But this might be that it was my fault. I wouldn't say that it was given by the circumstances. I don't think so. I mean I had only five or four of them the whole time. Five, I think. Yes, Planck had more, there is no doubt.

Kuhn:

Let me change to go just a little further on. You must have been back from Breslau and in Berlin again when the Bohr atom was announced.

Reiche:

Yes. I'm just thinking whether Ladenburg was already in Berlin at that time. Probably not. That's absolutely correct. When Bohr's papers appeared I was in Berlin.... I did not subscribe to the Philosophical Magazine. I cannot say exactly, who first told me about it. I think that Ladenburg, who might have been more extensive with everything, first wrote to me that there had appeared a very strange paper by a man of the name Niels Bohr. Then I had it at once. I had the English paper.

I think I wrote to Bohr and asked him if he had still a copy left, to send me one. I have it still, I am pretty sure. Yes, of course, very big astonishment.... And then very soon appeared the idea of the correspondence principle. I do not know exactly when it was first announced.... I can speak only of my own feeling. I understood it correctly only later. I then went back to the first paper and saw that he really begins already with this.... I recognized the importance of this, and the very fine arrangement of the paper, only, later when I became more familiar with the correspondence principle. Not to speak of the much later things which Kramers did. Well, I do not know, I will not interrupt too much. [laughter].... I think there were a lot of earlier trials made to find the Balmer formula. Nevertheless, I think nobody really succeeded. The most complicated things were invented or suggested to do these things. For instance, I do not know whether you know the name Byk, a physicist, half a physical chemist, but also a physicist.

I knew him also personally. He was a very intelligent and very sharpminded man, and he came to the idea that inside the atom the Euclidian geometry cannot be correct. It must be replaced by some of the nonEuclidian geometries. Of course he did not find the Balmer series, but at least some of the difficulties of the usual classical physics could be avoided by this. o orthree papers by him were published, but then the thing went down by oblivion completely.

Kuhn:

I wonder if you remember discussions about the Bohr atom in Berlin, remember reactions of other people?

Reiche:

I certainly recall corresponding about these with Landenburg, but I do not know whether the letters have survived. He was the man who influenced me the most in my interest in atomic physics, and also later in other things. I think I never discussed such questions with Planck. The bridge was again mostly due to his reticent character.... I know that there was at a certain time one of these big meetings in Goettingen. There was a big fund by a man of the name of Wolfskehl to invite famous physicists and so on. I attended of course - this big Lorentz Week - it was always a week- then came, I think, the next time the Planck Week; and I think then came the Bohr Week. So it must have been, I would say, in 1915 or something like that. There it was already extensively discussed. Everything. Through a whole week. But I cannot remember who in our physics colloquium in Berlin gave the talks about this....

Uhlenbeck:

What did you do during the war?

Reiche:

I was at first not taken into the military, because I was not strong enough. From '15 to '18 I was assistant to Planck. But even then what was my duty? My duty was to look through the papers which were written by the students and to correct them. I went out to see him every week and discussed the errors and so on with him, then I went back. That was really all, everything.... These papers were the problems which were given from week to week.... Of course I had to be present in his lectures again, and if students came to ask me questions in connection with the lecture I tried to answer them, That I came much closer to him personally - I mean now in the scientific sense - this I have the feeling was not the case. This failed through his inexpansive nature.

But it might be, also, that I feel it differently. I think my successor was, as far as I know, Lise Mitner, and I think that she was on really familiar terms with the family and also with the second wife, (Margo) Planck. She stood to him in a less formal way. There is no doubt about it. And Laue, obviously, too. So it might be that-but nevertheless, I mean I was in contact through - every week with him. After this time, yes, my highest military rank was what they called arbeitsverwendungsfaehig, "capable for doing work in a bureau." So this was my highest military rank, and I was then assigned for a certain time to one of the big factories in Berlin. (Auer) was a big factory which originally made these gas lights. A combination of rare earth and something like this.

There I tried with another colleague of mine, a chemist, to make some experiments on how to replace the gas masks, because the rubber was missing. We had no rubber, and therefore certain things, elastic things, were suggested.... But this went on only one year in 1919 - as far as I recall, after the war - I became a certain theoretical adviser, a kind of advisor to Fritz Haber in the Physical Chemistry Institute. There were again interesting and interested people, Ladenburg was there, and James Franck was there, and (Kallmann) was there. I worked there I think one year and a half or one year and three quarters, something like this. Then I got a call to Breslau as Professor. This was in '21....

Kuhn:

There seems to be very much more continuity of German science during the war, than there is in other European countries....

Reiche:

Lande was never in uniform. I remember seeing him. Born, was there with him, and they made together the cubic models of atoms. It was funny they had the time. I think they always had a big paper of this official thing on the desk, and below this they had the other things. If a colonel or somebody official came in, then, it was at once covered and they seemed to work for the war effort.... [After stopping for tea, the recording resumes during a discussion of Reiche's paper in Zeitschrift Fuer Physik 1 (1920) ,"Zur Theorie der Rotationsspektren."]

Reiche:

..... And when I had finished the thing and written it up it might be that I had already the galley proofs - a paper by Imes, from here, from America, appeared.

Uhlenbeck:

Yes, from Michigan?

Reiche:

And now I saw at once it was impossible. [R. at the blackboard]. It looks quite different, namely it looks in this way: the line was missing. The gap was double every other distance, And so it must be something like this. This never comes out of the old quantum theory, because you have here always this one here. Einstein was in Berlin at that time. I rushed to Einstein. He said "Who tells you that you have to quantize in this way? What about if you quantize in this way, to say not nh over two but n pIus 1/2 h^2.

Who tells you that it is not in the middle, that the quantum numbers are the integers and not the half integers?" And so I have always marked this, because this is the best one what my paper brought, there is no doubt. The paper showed that it is impossible to reconcile the new lmes experiments with the old quantum theory. And I have always marked this also as one of the points where the old quantum theory was in disagreement with the experiments, apart from other points which I also tried here to mark.

But it was one thing which usually has not been mentioned, that the vibrational rotational spectrum is really only in agreement with the experiments according to the new quantum theory, never with the old quantum theory...

I mention this because I remember you asked me the last time - I do not know whether it was here or when you had to wait for taxi - what the reason was, in my opinion, which compelled us to say the old quantum theory doesn't give everything, or gives some results which are wrong.... This paper [Ann. d. Phys.68 (1919)] is on the specific heat of hydrogen, the rotational part of the specific heat. There I tried - a lot of people have tried.... There are different possibilities mentioned, and computed, and different curves are given, and none of them worked! But I must say, this could not succeed, this could not! I mean there would have been necessary too ingenious a man to guess that it is a mixture. Nobody could guess this in advance. And all the trials which we tried out. There is not only one, but there is a lady, Miss Rotszayn.

Uhlenbeck:

You know Arnold Eucken? In the Lorentz' Festschrift, which appeared just in '25 he collected all the data. Eucken in desperation used quarter quantum numbers.

Reiche:

This I didn' t know.

Uhlenbeck:

1/4 and 3/4 and so on. He did everything, and there was not a single thing.

Reiche:

Sometimes one got good agreement for low temperatures and for very high temperatures, but in the middle the whole thing fails. Apart from those curves which went up and then again down. I do not know. It has, of course, a certain historical meaning, that we did it....

Uhlenbeck:

What did people think about it? Because it was such a flagrant failure.

Reiche:

Yes, a flagrant failure. Nobody could understand what to do. One excluded certain quantum states. Nothing was really succeeding. I do not know whether one doubted of the experiments. Even this of course was one of the possibilities. But Eucken's experiments were very good he was a very good experimental man. His observations were probably very exact.... [Looking through reprints of Reiche's papers]. This I would like to give you. This is the f sum rule, but not the original. Of the original I have only one. This is a little note by Thomas, alone in Naturwissenschaften. And then we both sat together and tried to find some consequences.

Uhlenbeck:

This is the dissertation?

Reiche:

My thesis, yes, my dissertation. But I have never tried or made the effort to really put it in relativistic form. I do not know why I did not do it. This was 1908, so I could do it then. The funny thing is that Planck did not say anything. The data is the change of the entropy in this [cylinder]. I think I pushed the semi-permeable plate down and back - as far as I remember. This gave an increase in entropy proportional to v^2/c^2 . However, as I've said already, I didn't use relativistic formula for the Doppler effect, and so on. I do not hope that a negative value would come out, but at least I am very suspicious about it.... Here are a few things about dispersion.... In this paper with Ladenburg it is so that we did not derive a consistent dispersion theory, in which instead of the revolution numbers the emitted lines came out. We thought it completely self-evident, that one had to change the denominator of the dispersion formula in such way that the frequencies were the emitted line frequencies, and not something which has to do with (the orbit).

Uhlenbeck:

But that was a big step, wasn't it?

Reiche:

But not in this direction. Only in the direction of explaining that the N which is on top of the dispersion formula the number of [dispersion] electrons. It never came out correctly equal to the number of atoms, or to the number of atoms multiplied by the number of electrons in an atom. It gave, under certain conditions, even numbers which are less than the whole number of atoms. They were written very often with a German N - [R demonstrates on blackboard]. This was the main aim of the whole thing.

There, based on a previous paper by Ladenburg, we found a relation between the German N and the real number of atoms. The f were not 1 or 2 or 3 or something like this, but could be point 5 or the like. And the explanation of this was the aim of this dispersion paper. But it did not come out that we had a correct and consistent theory in which the denominator gave now the emitted frequencies. This, I think, was only done by Kramers, first of all, Yes, Kramers and Heisenberg. What Kramers did was also before the quantum mechanics came out. It was in this reinterpretation period.... Under this period fails also this f' sum rule which Thomas found; and I think several more things, but these were probably the main things.

The application, then, of the sum rule to dispersion is an easy thing. I mean to the dispersion of X-rays. That was mainly, I think, the starting point of Werner Kuhn. He started directly while our Thomas, W. Thomas, derived it in quite a well, how he really found it I do not know... He came to me and said "Well, if you write down this and differentiate it with respect to an action variable J, then you get a relation which on the right hand side is one, or three or something like this." So I tried to reinterpret this (derivative) with respect to the action variable, and this is a difference. And if you do this with skill, then you get this and this relation for the f values, And this is Thomas-Kuhn. [Broken comments on various papers here omitted].

Uhlenbeck:

One always forgets that these things went so fast at that time Because also the distance between the matrix mechanics and the wave mechanics was to close,...

Reiche:

There was enormous enthusiasm about the Schrödinger paper, because of all those who had hope. "Now we are, thanks to God, back in classical physics, because it is like a string -" the differential equation with boundary conditions."

Kuhn:

How would you contrast that reaction with the Heisenberg - Born - Jordan - the matrix mechanics? Was there the same sort of enthusiasm for that?

Reiche:

The first Heisenberg paper was of great influence, at least. I remember I read it during the summertime vacation. I was with my wife in Lugano. There I met Carotheodory. I gave this Heisenberg paper to Carotheodory, who was quite enthusiastic. He said, "Well this is a completely new thing and very, very well explained, and a very reasonable idea." Of course he was a mathematician, I mean he was not a physicist, but be was very intelligent and very clever. And he at once grasped what the whole thing was. But nevertheless I would say the spread of enthusiasm among physicists was much stronger in the case of Schroedinger. Though unfortunately they misunderstood what was behind it, I have the feeling. Because actually Schroedinger then showed that matrix mechanics and his wave mechanics were absolutely the same.

Uhlenbeck:

Pauli showed it. He wrote it to Herr Schroedinger, because I think that's mentioned in one of the papers....

Kuhn:

But there was a strong initial feeling that this was classical physics again, because it was a wave equation?

Reiche:

Yes, this was a wave equation and completely welI known. A little different because the condition was at infinity and in infinite space, but on the whole one was back with familiar things.... And then came already very funny discussions by Schroedinger himself, who felt very well what he had meant, understood what he had meant.... I cannot completely remember, but I have the feeling I didn't know about De Broglie' s work before I was pushed by Schroedinger to read it. This was of course very, very impressive, De Broglie' s idea, De Broglie' s thesis. You got a new issue of Ann. d. Phys., the next paper by the man. And the third or fourth paper was very long about the Stark effect, or the relations in perturbation theory, and then came the dispersion theory.

One was in a kind of breathless reading. The first was - due to a funny beginning - the most unimpressive - if I can call it in this way. Everything was completely okay, but he started in a very funny way in the first. But in the next one he gave the big introduction and the relation to Hamilton theory. I remember that always when I then went back reading the first one was funny, gave a funny feeling. The next one went mostly into reminding us of De Broglie's idea.

Kuhn:

Had people been waiting for this? That is, people had already been saying by '23, '24 that there' s got to be a very different way to do things. More work in the same direction is not going to bring us out of these problems. Was that same feeling at Breslau?

Reiche:

I must say so, due to the repetition and repetition by Bohr "we cannot go back more to the classical." He always said that his correspondence principle just showed this, that it is a correspondence but it is not that quantum theory goes directly over to the other. That is, I think, what he repeated in his style. It is a little mysterious sometimes, a mystic style. I think influenced by this repetition by Bohr, one had, certainly, the feeling that it cannot go in this way as it went so far. That something quite new must still be found. At least I had, at first, that feeling also, arid it was certainly a deception that what Schroedinger did [appeared] in a certain way retrograde. Certainly this was only due to the original wave mechanics being in the form of a differential equation. [A discussion of the sorts of questions one may not ak within quantum mechanics is here omitted].

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