Institute for Theoretical Physics
Munich, December 17, 1926
Dear Dr. Noyes:
I had hoped that the enclosed paper on the Theoretic cal Prediction of the Physical Properties of Many Electron J and
Mole-refraction would reach you in time to act as a Christmas greeting. The delay arose from my having to type it myself,
for the typing agencies require double hourly price and also double time for typing in English. [Some of the keys on German
typewriters differ from ours, which explains why I occasionally put “ä” in place of “g”, etc.]
This paper will (unless some unforeseen circumstance arises) be sent to the Proceedings of the Royal Society in a few
days. I have not forgotten your advice regarding publication in our own journals. Professor Sommerfeld became a Foreign Member
of the Royal Society last spring, and I believe that he feels that he should submit some paper to the Society. I have felt
that his kindness to me required me to act in accordance with his desires. Moreover, I had been anticipating with considerable
lack of pleasure the arguments that the Physical Review would advance against the publication of such a long paper, and the
multitude of small but annoying changes that they would doubtless require to be made when (after several months) they had
decided to publish it. My first paper, which was to appear in the January issue, will not do so, for I was sent the proof
of a Japanese investigator’s paper, instead of mine. They haven’t reached a decision regarding the electron-affinity paper.
(I hear now that it is accepted)
I believe that this work is of considerable value, in showing the theoretical treatment of the properties of complicated
atoms and ions. The possible extensions and applications of the method are numerous; for example, I am now working on the
sizes of ions in crystals, and the question of the occurrence of the various types of crystals. This work, if it turns out
well, will be suitable for the Journal of the American Chemical Society, I think. I think that it is a very interesting that
one can see the ψ- functions of Schrödinger’s wave mechanics by means of the X-ray study of crystals. This work should be
continued experimentally; I believe that much information regarding the nature of the chemical bond will result from it, and
I am hoping that it might be possible to do the experimental work in Gates.
I feel that the theoretical (and experimental) study of the properties of complicated atoms and ions (i.e. with many
electrons) and of molecules could really be classed with chemistry; for usually a study of the different phenomena exhibited
by different chemical substances is called chemical, and the study of phenomene without especial reference to the chemical
substances exhibiting them is called physical. However, we can hardly class this with Physical Chemistry, as ordinarily understood;
possibly Molecular Chemistry would be a suitable description.
I wrote to Moe regarding my application a couple of months ago, making it very clear that I would have to have a decision
made about a renewal of my Fellowship in time to return to America if it were not granted. In reply he said nothing definite,
but said that I cam to send in a budget of my expenses before February 1. I am now preparing my application for renewal, a
copy of which I shall send you in a few days. My plans are the following: to leave here about February 15 for Gottingen, spending
about four weeks there, and then two weeks in Berlin. After that four or six weeks in Copenhagen, to learn the developments
made under Bohr and Keisenberg, who is a fine young man. Then we shall go to Zurich for the summer semester with Schrödinger,
who will have returned in May. Debye will be in Zurich only for the month of June, during which he will lecture. In August
we shall go to England, especially to visit W.L. Bragg in Manchester; and then home in September.
I am sorry to do so much traveling, for I like the repose of one locality, and I’m afraid that my work will not progress
very fast. However, I think it highly profitable for me to visit these important places, staying long enough in each to get
a pretty good idea of the work being done. I have enjoyed very much the two semesters with Professor Sommerfeld, who is a
fine teacher (in particular have I learned much mathematics in his seminar); and I’d rather like to stay longer. Traveling
is expensive, and perhaps the Guggenheim Board will not grant the entire amount of my budget (which I haven’t yet estimated),
in which case I’d have to omit part of my schedule.
I shall soon have Selmayr begin work on making our crystal models. I am sure that you will be pleased with them.
I am continuously surprised at the number of books continually appearing here – especially handbooks. We seem by contrast
to write very little in the United States. Every university has at least one chemist and one physicist who are more or less
authorities in some field, and who write about it in one of the many handbooks, such as the 23 (or more) volumed Handbuch
I am learning a good deal of the foundations of quantum theory from Sommerfeld, and I hope to get an idea of the opinions
of Bohr, Heisenberg, Schrödinger, and of others. Accordingly I am looking forward to being back at the Institute, and especially
to the Chem. Seminar. Sommerfeld told me that he would put out a new English edition as soon as he found time – I assume in
about a year. He will write two volumes, the first elementary, the second specialized. I am sure that the new quantum mechanics
will be in it, but I think that he himself has not yet decided upon how to include it, and upon how many changes to make over
the 4th edition. He said that it will be some time before he publishes another German edition, as the publishers still have
several thousand copies of the 4th edition on hand. Have I not mentioned before that he accepts completely the wave mechanics,
as a good mathematician would, for all quantum theory problems are thus reduced to the boundary conditions problems of the
old mathematical physics?
I hope to see the Travel Prize boys somewhere. Perhaps they will not reach Zurich before we arrive there.
The news regarding the people at Gates was most welcome. I read Prescott’s interesting paper; I would surely feel lost without
the Journal. A trip to Europe has served to show me, as well as Dr. Dickinson, that crystal structure still has a future before
J. I assume that Yost did not continue to work in crystal structures; I noticed that Robertson said that he and Yost were
going to measure absorption edges. It would be fine if they would, but I’m afraid that I must interpret your lack of mention
of it as meaning that Robertson merely put the reference in for effect.
I am glad the new edition of Chemical Principles is getting along well. I think it is a wonderful book. You know, of
course, that all my knowledge (which is not encylopedaic, but is good) of physical chemistry was obtained from that book,
and except for the last three chapters came from solitary study of the proof sheets you so kindly sent me. Have you prepared
the crystal section? I suppose that Dr. Dickinson will be of great assistance with it. I should glad to contribute something
(other than my mimeographed notes), if you desire me to.
P.S. December 28, 1926
We had a pleasant but not exciting Christmas, and remembered the most enjoyable time we had with you a year ago.
I kept this letter so as to be able to send a copy of my Fellowship application to you; I mentioned, you see, that I
am asking you and Dr. Millikan to write to them for me.
I have just realized that the time will soon be here when the Institute, we all as other universities, makes its decisions
regarding the staff for the next year; so that definite arrangements regarding my position and salary will also soon be made.
I have had no offers from any one, for I have thought, and accordingly expressed myself as believing, that I would return
to the Institute.
Most people seem to think that work such as mine, dealing with the properties of atoms and molecules, should be classed
with physics; but I (as I have said before) feel that the study of chemical substances remains chemistry even though it reach
the state in which it requires the use of considerable mathematics. The question is more than an academic one, for the answer
really determines my classification as a physicist or chemist.
I hope you are pleased with the paper I am sending you, and are not displeased that it has been sent to the Royal Society.