The two schematic biographies reproduced in this appendix have been chosen to illustrate the extent of material available in standard published sources. The first, that of Arnold Sommerfeld, indicates what can be learned about a prominent physicist for whom numerous obituary notices have been written; the second, which concerns James Franck, since deceased, gives an idea of the material available about a leading physicist and Nobel laureate during his lifetime. In the case of less distinguished living physicists, the amount of easily obtainable information seldom greatly exceeds that given in the schematic biographies appearing in Chapter II.

Both biographies are printed almost exactly in the form in which they were originally prepared, i.e. as rough working papers. Changes-e.g., joining sentences and phrases, deletion of superfluous words-have been introduced only to make reading easier and to reduce the total volume. Neither biography has been amplified or corrected with information acquired subsequent to its preparation. Sommerfeld's biography was one of the first undertaken, and contains no cross references to others drawn up by the project. The Franck biography was written somewhat later and includes information obtained during the course of preparing others. In general, biographies made up later have had the advantage of relevant material incorporated in earlier ones, but cross indexing was never entirely systematic.

SOMMERFELD, ARNOLD JOHANNES WILHELM (1868-1951)

Born December 5, 1868, Königsberg, Prussia, into a family of the German Evangelical Church. His mother was born Cäcilie Matthiass. (Vita in doctor's dissertation. Bib. 1891. ["Bib." refers to a bibliography of Sommerfeld's writings prepared in connection with this biography.] ) His father, Dr. Franz Sommerfeld, was a medical practitioner devoted to science and a passionate collector of natural objects like minerals, shells, amber, beetles. (*Royal Soc. Obit.* 8 [1952] : pp. 275-296, written by Max Born, henceforth [R.S.O.]).

Sommerfeld studied at Altstädtisches Gymnasium, where Hermann Minkowski, Max Wien, and Willy Wien were simultaneously in attendance, all slightly ahead of Sommerfeld. Sommerfeld was almost more interested in literature and history than in exact sciences and equally good in all subjects, including classical languages (RSO).

1886. Passed final examination at gymnasium (RSO). Entered Albertus-Universität Königsberg (Vita). 1886-90. After some irresolution Sommerfeld decided to stud mathematics, but also attended lectures on political economy and philosophy; the inspiration of the mathematical faculty kept him from changing universities, as was customary. When he attended Hilbert's lecture on the theory of ideal numbers, he came to believe that his interest was in the most abstract mathematics (RSO).

Teaching staff in department of mathematics at the time: Hilbert D., Privatdozent; Hurwitz, A. Extraordinarius (later at Edgn. Techn. Hochsch., Zurich, 1892-1919) ; Lindemann, F., Professor (RSO) (P-5 [the fifth volume of Poggendorff's *Biographisch-Literarisches Handwörterbuch der* *exakten Naturwissenschaften]*).
At the University Sommerfeld heard lectures by: Chun, Dahn, Elster, Hilbert, Hurwitz, Lindemann, Lossen, Pape, Rahts, Saalschütz, Thiele, Volkmann, Walter, Wiechert (Vita).

My time of study coincided with the period of Hertz's experiments. At first, however, electrodynamics was still presented to us in the old manner in addition to Coulomb and Biot-Savart, Ampère's law of the mutual action of two elements of current and its competitors, the laws of Grassman, Gauss, Riemann, and Clausius, and as a culmination the law of Wilhelm Weber, all of which were based on action at a distance. The total picture of electrodynamics thus presented to us was awkward, incoherent, and by no means self-contained.

Teachers and students made a great effort to familiarize themselves with Hertz's experiments step by step as they became known and to explain them with the aid of the difficult original presentation in Maxwell's* Treatise.
*
... It was as though scales fell from my eyes when I read Hertz's great papers: "Über die grundgleichungen der Elektrodynamik für ruhende Körper," (*Göttingen Nachr.,* March 1890). Quoted from Sommerfeld's *Electrodynamics,* pp. 1-2 (Bib. 1942).

Heinrich Hertz's great paper on the "Fundamental Equations of Electrodynamics for Bodies at Rest" has served as model for my lectures on electrodynamics ever since my student days (Sommerfeld, *Electrodyn.,* Preface).

For these reasons Sommerfeld was not inspired by the Professor of Theoretical Physics, R. Volkmann, but rather by the young Privatdozent Wiechert (RSO).

Emil Wiechert (born 1861; Dr. Phil., Königsberg, 1889; Privatdozent, Königsberg, 1890-97) is remembered for his suggestion in 1896 that Röntgen rays are transverse electromagnetic vibrations of short wave length (simultaneously with Stokes) ; for his calculations in 1897 of the charge to mass ratio of cathode rays from magnetic deflection experiments, simultaneously with J. J. Thomson (Whittaker, Vol. 1); and his name is attached to the relativistically correct retarded four-potential due to a moving point charge (Panofsky and Phillips, *Classical Electricity and* *Magnetism*).

1890. Wiechert and Sommerfeld devised a harmonic analyzer together (which was constructed) for reduction of a set of temperature measurements taken at a meteorological station in Königsberg. This and a paper on heat conduction which Sommerfeld wrote at that time but did not publish were intended as part of a prize competition for the best reduction of the data (RSO). This work was probably inspired by Wiechert who was later Professor of Geophysics at Göttingen (P-5).

Sommerfeld describes his own work on heat conduction as suffering from the characteristic attitude of this period to "stick to mathematical generalities" instead of studying the peculiarities of the problem and using numerical methods (RSO). [It is not clear whether this comment is also intended to include Sommerfeld's paper of 1894 (Bib., 1894).].

1891. Thesis: *Die willkürliche Funktion in der* *mathematischen Physik.
*
Sommerfeld conceived and wrote out the thesis. in a few weeks (RSO). It is dedicated to Ferdinand Lindemann.

1892. Sommerfeld says that his first attempt "to sail the high seas of theoretical physics proper" was "Mechanische Darstellung der elektromagnetischen Erscheinungen. . . " (Bib. 1892), which was stimulated by reading Wm. Thomson's works (RSO). He was soon convinced not much was to be gained by mechanical "explanations" of Maxwell's equations, but the paper gave him the satisfaction of attracting the attention of Boltzmann (RSO).

Passed examination for the teacher's diploma and then did his year's military service (RSO).

1893. In October Sommerfeld went to Göttingen; through the accident of personal connection he became assistant at the Mineralogical Institute under Th. Liebisch (RSO). Mineralogy was later of use in advising Laue (1912) .[Laue, *Naturw*. 38 (1951): pp. 513-5181.

1894. Sommerfeld became Felix Klein's assistant for the management of the Mathematical Reading Room and its library. He was responsible for working out Klein's lectures and producing a copy for use of the students in the reading room (Bib. 1896) (RSO).

Sommerfeld regarded Klein as his real teacher not only in pure mathematics, but also in his attitude to mechanics and mathematical physics: "Overwhelming was the impression which I received in lectures and discussions from Felix Klein's grand personality" (RSO).

Voigt offered Sommerfeld an assistantship in his laboratory; he declined, but with regret, the opportunity to do experimental work. Later felt he had made the right decision (RSO).

1894-95. Sommerfeld was working on his HABILITATIONSSCHRIFT for admission as a Privatdozent of Mathematics. It was to be the first (?) exact treatment of a diffraction problem. A preliminary report was published in 1894 and the full version in 1895 (Bib. 1894/95/96).

Progress on the paper was followed with interest by the Professor of Theoretical Physics at Göttingen, W. Voigt, and the results were later us used by him; Poincaré took up this "méthode extrèmement ingénieuse" and it is regarded as a classic today (RSO).

1895. Sommerfeld attended the Naturforscher Versammlung at Lübeck where he gave an account of his work on diffraction (Bib. 1895). Sommerfeld relates that at Lübeck, following a paper favoring Energetics, a discussion between Wilhelm Ostwald and Ludwig Boltzmann took place and that Klein and he, just as all the younger mathematicians, sided with Boltzmann [Flamm, *Alman. Akad. Wien (1952)* : p. 351].

1895-96. A series of lectures by Klein was the starting point of *Die Theorie des Kreisels (RSO).
*Pauli points to the connection between the Cayley-Klein matrices and *Theorie des Kreisels* and the two component spinors of wave mechanics [Pauli, *Zs. Naturf,* 6a (1951): p. 468].
*Theorie des Kreisels* reflects Sommerfeld's change in attitude towards mechanics in general from mathematical in the first two volumes to physical and intuitive in the last two (RSO).

1895-97. Sommerfeld was Privatdozent for 5 semesters and lectures on Probability, Projective Geometry, "Flächentheorie," Calculus of Variations (Laue, *Naturwiss)* Partial Differential Equations of Physics (Born, RSO).

Sommerfeld became a good friend of Drude of Göttingen, but had no contact with Nernst (Laue, *Naturwiss.,* p. 517).

1897. Married Johanna Höpfner, daughter of Kurator Dr. Ernst Höpfner of Göttingen University (Born, RSO).

H. S. Carslaw spent summer semester studying in Göttingen and conversed much with Sommerfeld [E. Lampe, *Fortschr. d. Phys.* 55: p. 3791, and Sommerfeld published a paper in an English mathematical journal (Bib., 1897).

The first volume of *Theoric des Kreisels* appeared (Bib., 1897).

Sommerfeld was appointed Professor of Mathematics at the Mining Academy in Clausthal in the Harz Mountains. He was Willy Wien's successor in this chair [Thirring, *Acta Phys.* 2 (1949) : p. 222]. Sommerfeld lectured mainly on elementary Mathematics (RSO).

1898. Sommerfeld edited the index to Vol. 150 of *Math. Annalen.
*
He attended the Naturforscher-Versammlung at Frankfurt where he reported on his work on the propagation of electromagnetic waves along wires (Bib., 1898).

1899. Sommerfeld published a full paper on propagation of electromagnetic waves along wires. Born points out that: (a) Hertz treated infinitely thin wires; (b) Poincaré, J. J. Thomson, Rayleigh, Drude had only partial success with finite diameter; (c) Sommerfeld obtained the first rigorous solution (RSO).

Sommerfeld published the first in a long and irregular series of papers on Röntgen rays as narrow electromagnetic pulses and the diffraction effects to be expected in consequence (see Bib., 1899, 1900, 1912, 1915).

While in Clausthal he became editor of Vol. 5 (Physics) of *Enzyklopaedie der math. Wiss.*, founded and directed by Klein (Born, RSO). A big job; it took much time for a long period and was not finished until 1926, by which time Pauli had a hand in it. Sommerfeld met with Boltzmann at editorial sessions of the *Enzyklopaedie. These* meetings made a strong impression on Sommerfeld [Flamm, *Alman. Akad. Wien* (1952), p. 3521.

1900. Sommerfeld accepted chair of technical mechanics at the Technische Hochschule, Aachen, and was thus compelled to concentrate on technological problems. At first distrusted by students and colleagues as a mathematician, he was soon elected to the technological society and consulted as an expert (RSO).

Began work on hydrodynamics in connection with technical problems (Bib., 1900). Sommerfeld was to retain his interest in this field for a long time see, for example, Heisenberg's doctoral thesis (1923).

1901. Sommerfeld published a long summary paper on the diffraction of X-rays (Bib., 1901).

1902. Sommerfeld published a paper on the dynamic loading of columns (applicable to reciprocating engines, etc.) and one oh the theory of the braking of railroad trains.

1903. September. Sommerfeld read a paper to the Naturforscher-Versammlung at Kassele on the scientific results and goals of modern technical mechanics. This was considered an important statement and was translated into English in *Math. Gazette* (Bib. 1903). He became one of the foremost supporters of Klein's program to fertilize German technology by intuitive presentation of mathematical methods (Born, RSO).

1904. Sommerfeld published a paper on the oscillation of dynamos (?) connected in parallel (Bib. 1904).

Max Wien, who was Sommerfeld's colleague at Aachen, stimulated him to consider the problem of the increase in resistance of a wire to alternating current when wound in a coil (Flamm) (Bib., 1904 and 1907).

Sommerfeld's most important technical paper was a hydrodynamical theory of lubrication. He seems to have particularly enjoyed this evidence of the power of mathematical physics applied to a subject which was previously regarded as inaccessible to exact reasoning (Born, RSO) (see Bib. 1904).

Not all of Sommerfeld's work in this period was devoted to technical problems. He continued work on the *Enzyklopaedie,* publishing two articles in it in 1904 with R. Reiff (Bib., 1904), one of these on action-at-a-distance.

*By far the largest and most important work* in *this period was a series of papers on electron* *theory* (see Bib. 1904-05).

Sommerfeld contributed to the *Boltzmann-Festschrift* (Bib., 1904).

1905. Sommerfeld published a number of technical papers.

1906. *The call to Munich. * There is some disagreement about the politics of this appointment. Laue's version, although the less flattering, is the more plausible (Laue, *Naturwiss.,* p. 515): Röntgen, having the experimentalists' characteristic distrust of theoreticians, kept Munich from offering the chair of theoretical physics for 7 years after Boltzmann left in 1899. In 1906, however, Munich offered the chair to H. A. Lorentz. Lorentz declined and suggested Sommerfeld instead, having been impressed by the series of papers on electron theory. This explanation is corroborated by G. L. de Haas-Lorentz's assertion *[H. A. Lorentz* (Amsterdam: N. Holland, 1957) ] that her father was offered the Munich chair. The other view is that Sommerfeld was Röntgen's choice. For example:

.... the farseeing initiative of W. C. Röntgen, who called Sommerfeld to Munich. (Pauli, *Zs. Naturf., p.* 468.)

It was Röntgen, the mighty man in the philosophical faculty, who insisted that Sommerfeld would be a worthy successor to Boltzmann [Ewald, *Nature 168* (1951): p, 365].

Relevant to this issue is Sommerfeld's tribute to Röntgen:

Looking back over my years of teaching I wish to acknowledge with gratitude my special indebtedness to two men, Röntgen and Felix Klein. Röntgen not only created the external conditions for my professional activity by calling me to a privileged sphere of action; he stood by my side and actively furthered the increasing scope of my work over a period of many years (Preface to *Lectures on Mechanics,* 1942).

Born, who had all this material available when he wrote his obituary, makes no mention of the issue, only noting that in 1906 Sommerfeld *was* *called* to Munich.

P. Debye was Sommerfeld's assistant at Aachen when Sommerfeld received a telegram from Röntgen concerning his new appointment. He said, "Debye, we have a call to Munich" (Sommerfeld, *Amer. J. Ph .,* 17 (1949) : p. 315).

Sommerfeld told Laue that Klein, whose heart was in mechanics, was not greatly pleased at the loss which this field suffered when Sommerfeld left Aachen for Munich (Laue, *Natuwiss.*, p. 515).

The Institute for Theoretical Physics at Munich had a workshop and some instruments, which appeared to some as self-contradictory. The apparatus justified itself by the experiments of (a)
Hopf on Reynolds numbers and (b) Friedrich and Knipping [Ewald, *Nature* 168 (1951): p. 365].

With the publication of Einstein's first paper Sommerfeld "burned his boats" (three large papers on electron theory, 1904-05) and became a convinced relativist (RSO).

1907. Sommerfeld became involved in a dispute with Lindemann (to whom Sommerfeld had dedicated his thesis and who was now at Munich too) over electron theory (Bib., 1907).

At the Naturforscher-Versammlung at Dresden Sommerfeld read a paper entitled "Ein Einwand gegen die Relativtheorie der Elektrodynamik und seine Beseitigung," discussing circumstances when phase velocity is greater than c. This is the first of a number of papers by Sommerfeld and his student L. Brillouin on phase, group, signal and energy velocity (Bib. 1907, 1912, 1914).
1908. Sommerfeld attended an international mathematical congress in Rome and read a paper of which Heisenberg says (*Naturwiss.,* 1951) that it forms even today the basis for investigations of the stability of laminar fluid flow (see Bib., 1909).

Sommerfeld deeply impressed by Minkowski's lecture at the Naturforscher-Versammlung on four-dimensional representation of relativity (RSO). He lectured on relativity after hearing Minkowski (Flamm).

1909. Relativity included in Sommerfeld's lectures on Electrodynamics (Ewald).

September. Sommerfeld read a paper at the Salzburg Versammlung arguing for Minkowski's approach to relativity (see Bib., 1909). Here Sommerfeld met Einstein: ". . . an occasion memorable to many of us through the atmosphere of the modest triumph of having conquered the obstacles which had prohibited progress of electrodynamics for so many years" (Born, RSO).

[Born dates this meeting in 1910 and hence after or concurrent with the publication of Sommerfeld's two big papers on the four dimensional formulation (see below). But internal evidence and the fact that the "triumph" was "tempered by Minkowski's early death," which occurred in January, 1909, makes 1909 more reasonable.]

Sommerfeld spoke of Einstein (the creator of the two relativity theories) only with the greatest "Verehrung und Bewunderung" [Pauli, *Zs.* *Naturf.* 6a (1951): p. 468].

Sommerfeld wrote a paper on the intensity distribution of Röntgen rays critical of Stark and light quanta (Bib., 1909).

According to Born, the papers on X-ray intensity distribution *(Phys. Zs.,* 1909, 1910) dominated the subject until the appearance of quantum mechanics. Sommerfeld stressed physical interpretation-mathematics quite elementary. He was perfectly clear that "Bremsstrahlung" was only one part of the total X-ray emission the other being the characteristic radiation discovered by Barkla (Born, RSO).

Sommerfeld wrote a paper on propagation of radio waves (*Ann. d. Phys.,* 1909) which was for a long time the standard theoretical work; it distinguished space and surface waves (energy flow as 1/r^{2} and 1/r, respectively). Weyl insisted the distinction was unphysical but Sommerfeld retorted *(Ann. d. Phys.,* 1920) that Weyl's method obtained no new results (RSO).

Ludwig Hopf (born 1889) received his degree under Sommerfeld, worked on hydrodynamics and collaborated with Sommerfeld on the paper on the integral representation of Bessel Functions (Bib., 1911). He died in Dublin in 1939.

Fritz Noether received his doctorate at Munich in 1909; he was author of the fourth volume Of *Theorie des Kreisels (1910).
*
1910. Rudolf Seeliger (born 1886) received his degree as Sommerfeld's student. He was Professor of Theoretical Physics at Greifswald, 1918-55.

Sommerfeld published two large papers on four-dimensional vector algebra and analysis, obtaining the four-dimensional formulation of Maxwell's equations and treating the "hyperbolic" motion of an electron (RSO; Bib., 1910). Sommerfeld suggested "four vector" and "six vector" in place of Minkowski's colorless terms " [vectors of the] first and second kind" (Born, RSO). The imaginary time coordinate, x_{4} *= ict.* was Sommerfeld's innovation [Scherzer, *Phys. Blätter* 7 (1951) : pp. 222-224].

1911. Sommerfeld wrote a paper on application of vector analysis to geometrical optics *(Ann. d.* *Phys.,* 1911) with Iris Runge, daughter of Carl Runge. The method of deriving ray optics from wave optics was later known under the name W. K. B. method (Born, RSO).

Paper with Hopf (Bib., 1911). The integral representation of the Bessel (Zylinder) functions laid the basis for Sommerfeld's predilection for complex integration, which played a great role in his seminar a decade later (Heisenberg, Natur*wiss*). He energetically pointed out the English literature on this subject, which had not received due attention in Germany before that time (Laue, *Naturwiss*., 1951).

Sommerfeld published a long paper on gamma rays as "acceleration radiation" accompanying ejection of a beta-ray (Bib., 1911).

Sommerfeld published his first work on quantum theory (Born thinks he entered the field rather late) (RSO).

Fall. Sommerfeld attended the first Solvay Congress where he delivered a paper emphasizing (for the first time?) that Planck had introduced a quantum of action, not energy (Bib., 1911). He gave a similar paper at the Karlsruhe Versammlung in the same year.

Wilhelm Lenz received his degree as Sommerfeld's student. He was Professor and Director, Inst. for Theoretical Physics, University of Hamburg, from 1921 until his death in 1956.

1912. Wave vs. corpuscular nature of X-rays. was a very controversial problem. Sommerfeld used a newly invented microphotometer (Koch) and again calculated the width of X-ray pulses. (Born, RSO). Laue, a Privatdozent at the Institute, told Sommerfeld his idea and suggested that Sommerfeld investigate it. Sommerfeld had an experimentalist assistant (Friedrich) whom he offered to Laue (Born, RSO). Sommerfeld was always rightly proud that the discovery of X-ray diffraction (Laue) had come from his theoretical department (Born, RSO).

P. P. Ewald (born 1888) received his degree as Sommerfeld's student. Sommerfeld had suggested to Ewald that as his doctoral research he investigate the behavior of electromagnetic waves of *optical* frequency in a *lattice of atoms* (it was in subsequent discussion with Ewald that Laue got his idea of *X-ray diffraction*) (Pauling,* Science,* 1951). Since 1949, Ewald has been professor at Brooklyn Poly.

1913. Sommerfeld published an article with O. Frank (a colleague at Munich) in *Zs. f. Biologie* (Bib., 1913). He also published a long classical treatment of the Zeeman and Paschen-Back effects.

Paper with Debye (see Bib., 1913) on photoelectric effect attempts an explanation emphasizing the quantum of *action. * Born says (RSO) "a wild adventure and quite out of date."
(The "well-known" Einstein relation, h_{v} = 0.5mv^{2} - ef
, although published in 1905, evidently had to wait until Millikan's measurements in 1916 for data sufficiently accurate to "establish" it. As indicated by his attempts at a classical electromagnetic theory of X-rays and gamma-rays, Sommerfeld viewed light quanta with distaste.)

Rutherford and Thomson atom models much discussed in seminar and conversation at Munich (Laue, *Naturviss.)* (Born, RSO).

Brillouin says: "I happened to be in his [Sommerfeld's] office when he opened the issue of the *Philosophical Magazine,* which had just arrived; he glanced through it and told me, 'There is a most important paper here by N. Bohr, it will mark a date in theoretical physics"' [L. Brillouin, *Wave Propagation and Group Velocities (N.Y.,* Academic Press, 1960)].

1914. Published a paper on Voigt's theory of the Zeeman effect, and technical papers on lubri,cation and electric arcs (Bib., 1914).

Landé and Epstein received their degrees. (Alfred Landé, born 1888, has been at Ohio State U. since 1931. Paul Sophus Epstein, born 1883, Warsaw, M. sci. 1909 Moscow, Munich after 1911, has been at Calif. Inst. Tech. since 1921).

1914-15. Sommerfeld lectured on generalization of Bohr's model to elliptic orbits (Laue, *Naturwiss.*, 1951).

1915-16. Sommerfeld published his major papers on dispersion theory on the Bohr model and the generalization of Bohr's theory, including relativity (Bib., 1915/16). The fine structure constant appears for the first time in these papers (RSO).

Sommerfeld formula for the relativistic fine structure of the hydrogen-like spectra, re-established by Dirac's wave equation, was generally considered to be one of the few lasting achievements of theoretical physics. Modern experimental techniques (Lamb and Rutherford) revealed that even this result was not final (Born, RSO).

Sommerfeld calculations of the hydrogen fine structure (1915) were used to decide experimentally (Paschen and Houston) between relativistic and electromagnetic increase in mass of the electron [Flügge, *Angew. Chemie* 69 (1952): p. 39]. (The historical connections in Flügge's statement are unclear: Houston was fifteen in 1915 and did not get to Munich until 1927!)

1917. Sommerfeld called to the University Institute for Theoretical Physics at Vienna (Born says 1916). He negotiated with Vienna but finally decided to stay at Munich (Flamm). He felt Munich was the right place because (a) he could lecture on disputed problems; (b) his seminars and colloquia attracted young scholars from faraway places and made Munich a center for theoretical physics (Born, RSO).

Sommerfeld published a paper on the intensity of spectral lines (Bib., 1917).

Karl Glitscher received his degree as Sommerfeld's student.

1918. Sommerfeld published papers on dispersion theory and on the application of his extension of Bohr's theory to X-rays (Bib., 1918). According to Born, this work gave a complete analysis of complex X-ray spectra and the results have remained the backbone of the theory of X-rays (RSO).

*1919. Atombau* published (Bib., 1919).

Sommerfeld and Kossel read a paper enunciating the "Verschiebungssatz" relating spark and arc spectra (see Bib., 1919) (Walter Kossel, Dr. nat. phil., Heidelberg, 1911, a student of Lenard).

September. Sommerfeld in Copenhagen lectured on an analogy between band spectra and atomic spectra (Bib., 1919).

1920. Sommerfeld introduced (*Ann. d. Phys.,* 1920) a new quantum number (the "inner quantum number") in order to explain the appearance of doublets and triplets (discovered by Rydberg). He used it to disentangle the anomalous Zeeman effect (*Zs. f. Phys.,* 1922) and to obtain from quantum mechanics a formula given by Voigt (Born, RSO).

A series of papers between 1915 and 1920 made Sommerfeld at once the leading theoretical spectroscopist, who had brought order and sense into meaningless chaos (Born, RSO).

Erwin Richard Fues, born 1893, received the "Doctor rerum naturalium" as Sommerfeld's student. Since 1947 he has been Professor at Stuttgart.

Adolph Kratzer, born 1893, Dr. phil., 1920, and Privatdozent, 1921, at Munich. Professor of Theoretical Physics at Münster, 1922 to date.

1921. Sommerfeld published papers on lubrication, the second order Stark effect, and X-ray fine structure (Bib., 1921).

Sommerfeld also published a vigorous reply to Stark's criticism of the Bohr theory of light emission (Bib., 1921).

Sommerfeld and Wentzel published a paper on "regular and irregular doublets" (Bib., 1921). Gregor Wentzel, born 1898 in Switzerland, received his degree under Sommerfeld and remained at Munich as Privatdozent, 1922-26. Since 1948 he has been at Chicago.

Wolfgang Pauli, Jr., born 1900, received his degree under Sommerfeld.

1922. Sommerfeld published two papers with Heisenberg on the fineness and intensity of spectral lines (Bib., 1922) and edited a collection of original papers on relativity by Lorentz, Minkowski, Einstein and Weyl (Bib., 1922).

Sommerfeld was using his inner quantum number to disentangle the complex spectra of chromium, manganese and the like (Bib., 1922/ 23).

Sommerfeld derived from quantum theory formulae for the anomalous Zeeman effect, previously obtained by Voigt from a classical model (Bib., 1922).

Sommerfeld traveled to Spain (Ewald), and to the United States. When he was lecturing at Harvard University on the selection rules (for l and j), F. A. Saunders, who was present, confirmed with satisfaction, that certain combinations of singlet and triplet terms for which he had looked in vain in the Ca spectrum were impossible because of these selection rules [Sommerfeld, *Science* 113 (1951), p. 87].

1922-23. Sommerfeld was Carl Schurz Professor at Madison. Here he met and became the friend of many distinguished American physicists (RSO), including Compton, whose discovery was announced at this time *(Bull. Natl. Res. Council,* 1922). Sommerfeld immediately recognized its importance, in contrast to many significant experimental- physicists of the twenties [Bechert, *Experientia 1* (1951) : p. 478].

Many American students were attracted to Munich during the years following Sommerfeld's trip to the U. S. [Pauling, *Science* 114 (1951): p. 383]

1923. The English translation of the third ed. (1922) of* Atombau* appeared and was widely adopted in the U. S. and elsewhere as a textbook for advanced courses (Pauling).

Sommerfeld published four papers in the *J. Opt.* *Soc. Amer.;* he discusses the arranging of electron orbits in the helium atom (Bib.,1923).

Sommerfeld wrote two papers on the magneton (the final victory of Bohr over Weiss) and regularities in the distribution of "magneton numbers" over the periodic table (Bib., 1923).

Heisenberg, born 1901, received his degree. In 1927 Heisenberg became Professor and Director of the Inst. for Theoretical Physics, Leipzig, where he stayed until the war.

1924-25. Sommerfeld published several papers on the intensity of spectral lines employing his inner quantum number, including one with H6nl (Bib., 1925). Helmut Hönl, born in 1903, Dr. phil., Munich, 1926.

E. Guillemin and V. Guillemin (Electrical Engin. and Biophysics, respectively) each spent a year in Munich. Now at Mass. Inst. Tech. and Harvard U.

Heinrich Ott, born 1894, received doctorate at Munich and stayed on as Sommerfeld's assistant; Privatdozent until 1929.

Sommerfeld, immersed in the empirical facts and their interpretation in terms of quantum numbers, was not so much troubled by the inconsistencies and inadequacies of the current quantum theory (RSO) [see, however, paper by Sommerfeld and Heisenberg, *Zs. f. Phys. 10* (1922)].

*Quantum Mechanics:* Sommerfeld did not take part in the overthrow of the old quantum theory, but he did adopt quantum mechanics enthusiastically, of course in Schrödinger's form (wave equation and eigenvalue problems). He assimilated the new methods and applied his extraordinary mathematical skill to many problems (Born, RSO).

1926. Sommerfeld published a number of papers on atomic structure and spectroscopy including readjustments necessitated by the spinning electron and wave mechanics. His collaborators were H. G. Grimm, A. Unsöld, and O. Laporte (Bib., 1926).

Hans A. G. Grimm, born 1887; Ph.D., Munich, 1911, a student of Heiduschka; Privatdozent, Munich, 1924-27. Since 1947 Honorary Professor at Munich.

Albrecht Unsöld, born 1905; Ph.D., Munich, 1927. Later work largely in astrophysics.

Otto Laporte, born 1902; Ph.D., Munich, 1924; Ann Arbor, 1926 to date.

Walter Heitler received his degree as a student of Herzfeld and Sommerfeld. Between 1933 and 1949 he was at Bristol and Dublin, and since 1949 at Zurich.

In the spring, Sommerfeld visited Great Britain, lecturing at Oxford, Cambridge, Edinburgh, Manchester and London (RSO and Bib., 1926).

Linus Pauling heard Sommerfeld's first lectures on wave mechanics (proper dating uncertain) [Sommerfeld, *Amer. J. Phys.* 17 (1949): p. 315].

Pauling received his degree in chemistry from Cal. Tech. in 1925; then Guggenheim fellow at Munich, Zurich and Copenhagen, 1926-27.

In place of Schrödinger's operations with loop integrals, Sommerfeld introduced the polynomial method for ascertaining eigenvalues and eigenfunctions [Flamm, *Alman. Akad. Wiss. Wien* 102 (1952) : pp. 347-571 (dating uncertain).

1927. Sommerfeld refused a call to Berlin (Planck chair) (Heisenberg).

Sommerfeld lectured on the application of Fermi statistics to metals (Ewald).

September. Sommerfeld announced his work on the quantum theory of the free electron gas at the Volta Congress at Como (Flamm). The meeting was well attended (Bohr, Born, Lorentz . . . . ) (see Bib., 1927).

An outline of the results was published in *Naturwiss.* (1927) (Bib., 1927) and a full development in *Zs. f. Phys.* (1928), along with a paper each by Eckart and Houston on the topic (Bib., 1928).

Carl Eckart, born 1902 in St. Louis; Ph.D., Princeton, 1925; Guggenheim fellow, 1927-28. At Scripps Inst. of Oceanography as of 1960.

Wm. V. Houston, born 1900 in Ohio; Ph.D., Ohio State, 1925; also a Guggenheim fellow, 1927-28. President of Rice Inst., 1946 to date. 1927-28. In Munich at this time were:

Rudolf Peierls, born 1907, Berlin, who studied at Munich before receiving his degree at Leipzig in 1929.

Edwin C. Kemble, born 1889; Ph.D., Harvard, 1917; Guggenheim fellow at Munich and Göttingen, 1927.

At a brief summer session, Sommerfeld has as students (Sommerfeld, *Amer. J. Phys.):* I. I. Rabi, born 1898 in Austria; Ph.D., Columbia, 1927; fellowships 1927-28, 1928-29, studied at Hamburg, Zurich, Munich, Copenhagen, Leipzig.

E. U. Condon, born 1902; Ph.D., University of California, 1926; traveling fellow at Munich and Göttingen, 1926-27.

1928. Hans A. Bethe, born 1906 in Strasbourg, received his degree at Munich. Sommerfeld had suggested the observations of Davisson and Germer, whose theory at that time was in quite an unsatisfactory state, for Bethe's thesis (Sommerfeld, *Amer. J. Phys.).
*
1928-29. Sommerfeld published some further papers on the electron theory of metals. In 1929 he began a series of papers returning to the question of the continuous X-ray spectrum and its angular distribution (see Bib., 1909-1910), but now employing wave mechanics (Bib., 1929, 1931, 1932, 1935).

Sommerfeld sailed around the world. In 1928 he was a visiting Professor at Calif. Inst. Tech. (Pauling) and lectured in Japan and India (RSO).

*1929. Wellenmechanischer Ergänzungsband* *für Atombau* was published (Bib., 1929). The two volumes of *Atombau* contributed more than any other book to make the new methods familiar to the physicist (Born, RSO).
*
*N. H. Frank, born 1903, *Dr. sci. Mass. Inst. Tech.*, 1926, was studying in Munich. He has been at M.I.T. to date.

1930. Philip M. Morse, born 1903; Ph.D., Princeton, 1929, was a traveling fellow at Munich and Cambridge, 1930-31

Herbert Fröhlich, born 1905, received his degree at Munich. Fröhlich left Germany for England in 1933.

Sommerfeld attended the Volga Congress (Ewald).

He published a paper with G. Schur on the distribution of photoelectrons (Bib., 1930).

1931. Sommerfeld at Ann Arbor (Ewald).

He published a 40-page review article (*Rev. Mod. Phys.* 3) with N. H. Frank on electron theory of metals (Bib.).

October. Sommerfeld attended a Nuclear Physics Congress in Italy (Rome?) (Bib., 1931).

He published a short note with Bechert on mechanical analog of diatomic molecules.

Karl Bechert, born 1901, had received his degree at Munich in 1925 and stayed on as Sommerfeld's assistant, 1926-33.

Otto Scherzer, born 1909, received his degree as Sommerfeld's student. Returned as Sommerfeld's assistant and Privatdozent, 1934-35.

Joseph Meixner, born 1908, was a student of Sommerfeld 1926-31, and Dr. phil. 1931.

Friedrich Maue, born 1908, received his degree under Sommerfeld, 1931. He returned as Sommerfeld's assistant and Privatdozent, 1933-45.

1932. Sommerfeld was disturbed by the rise of the nationalistic movement among students and lecturers (Dozenten) in the twenties. This movement had already led to difficulties at the University. (Heisenberg, *Naturwiss.*)

Sommerfeld published a series of papers on the Thomas-Fermi statistical model of the atom (Bib., 1932, 1933).

1933. Sommerfeld was in Edinburgh (James Scott lecturer) (Bib., 1933).

The article on the electron theory of metals for the second edition of the Geiger-Scheel *Handbuch der Physik* was written by Sommerfeld and Bethe. This piece has the status of a classic and has been reprinted and translated, even as recently as the 1950s.

Bethe had returned to Munich (after an absence of two years) as a lecturer, 1930-33.

Walter Henneberg, born 1910, received his degree at Munich. Since 1933 with the Allg. Elektr. Ges.

1934. Sommerfeld published a few articles on the electronic theory of metals extending and amending the *Handbuch* articles (Bib., 1934).

1935. Sommerfeld reached the age limit of 67 and, formally, had to retire; no successor was appointed and Sommerfeld was asked to continue teaching (Born, RSO).

He published two articles with A. W. Maue -- an approximate solution of the Dirac equations, and an extension of the Bremsstrahlung calculations to arbitrary energy (Bib., 1935).

He published an article with B. W. Bartlett patching up Sommerfeld's magneto-resistance calculations to encompass longitudinal effect.

Col. Boyd W. Bartlett, born 1897, a graduate student of West Point, Ph.D. Columbia, 1933. At Munich, 1934-35. Since 1942, Professor at West Point.

1936. Sommerfeld predicted "Raman lines" in Compton-scattered monochromatic X-rays (see Bib., 1936).

He published an article entitled "Über die Klein'schen Parameter a , b , g , d , und ihre Bedeutung für die Dirac-Theorie" (Bib., 1936).

1937. Sommerfeld published a short review article on the specific heat of metalic electrons. He also published his prediction of the X-ray Raman effect in a German journal, followed by a longer paper on the topic by W. Franz (Bib., 1937).

1937-38. Sommerfeld became interested in some cosmological proposals of Kothari (Bib., 1937, 1938).

The initial paper in a pair entitled "Künstliche Grenzbedingung in der Wellenmechanik" was published with H. Welker (no biographical data available) (Bib., 1938). The second paper was published with H. Hartmann in 1940 (Bib.).

1938. Heisenberg (*Naturwiss*.) asserts that Sommerfeld withdrew from his teaching position in this year owing to conflict with the Nazis. Born (RSO) appears to put it off until 1940. Hund (private communication) points out that seventieth birthday celebrations were held outside university, confirming Heisenberg. Sommerfeld evidently gave a lecture in Zurich (Bib., 1938).

1939. Sommerfeld published one of a number of papers on systems of units for electromagnetism (Bib., 1939).

Sommerfeld wrote with L. Waldmann an article for the *Hand- und Jahrbuch der chemischen* *Physik* on quantum statistics (Bib., 1939).

1940. Sommerfeld published a brief review of the history of the hydrogen fine structure and a proposal for determining electron distributions in metals from X-ray patterns, in *Naturwiss. (Bib.,* 1940).

Born relates that Sommerfeld was succeeded at Munich by a man from the Nazi ranks, whom Sommerfeld called the "worst possible successor" (RSO). After the war the usurper disappeared (RSO).

Sommerfeld was forbidden to enter the Munich Institute (RSO). However, he preserved his equanimity and showed no traces of bitterness (Born, RSO).

During the Nazi period, Sommerfeld occasionally said in discussion that it was not necessarily he who loudly makes known his intention who achieves the most for his fatherland, but that perhaps stronger and happier results follow from the one who serves a good cause without making a fuss over the obvious connection with his homeland [Heisenberg, *Naturwiss.* 38 (195 1), p. 338].

1941. Sommerfeld published a paper on the hydrogen fine structure.

1942-1951. During these years Sommerfeld spent most of his time arranging his lectures for publication (Bib., 1942) (Heisenberg).

1951.* The accident. * Sommerfeld was out walking with his two grandchildren one evening. He lost them at an unexpected turn and stepped into the street without looking. He was struck and dragged by a car [Jordan, *Jahrb. Akad. Mainz* (1951), p. 145].

*Personality*

If the distinction between mathematical and theoretical physics is significant, Sommerfeld was a mathematical physicist. His gift was not in divining new principles or in a daring combination of fields, but in deriving consequences of established or problematic theories. In his spectroscopic period he divined mathematical relations from experimental data. Epistemology and metaphysics connected with quantum mechanics were not in Sommerfeld's line.(Born, RSO).

Planck once indicated the relation between Sommerfeld and himself with the little verse:

Was ich gepflückt, was Du gepflückt,

Das wollen wir verbinden;

Und da sich Eins zum Andern schickt,

Den schönsten Kranz drauswinden [Laue,Naturwiss.38 (1951) : p. 518.]

*Personal Data*

Sommerfeld evidently had a younger brother or perhaps cousin. The following information was obtained from *Wer Ist's*, 1922:

Ernst Sommerfeld, born 1877, in Königsberg. At. tended Königsberg University and Göttingen. Assistant in the Mineralogical Inst. at Göttingen (as Arnold had been in 1893, "through the accident of personal connections"). Professor of Mineralogy at Aachen (1910) and Brussels (1911).

Children: Dr.-Ing. Ernst Sommerfeld, Pfarrersfrau Margarete Hoffmann, Dr. Med. Eckhart Sommerfeld [the order in which they were given by Flamm]. A third son did not survive Sommerfeld (RSO).

Sommerfeld had a happy family life whose warmth was always felt by whoever entered the hospitable Sommerfeld house (Heisenberg, *Naturwiss., Obit.).
*
Sommerfeld was hard of hearing and in his last years wore a hearing aid (Flarnm).

*Sommerfeld as a Teacher*

Born's successor at Göttingen was a graduate zoologist who by chance attended one of Sommerfeld's lectures, gave up his subject and became a theoretical physicist (Born, RSO).

Although after the first lecture a student might say, "the professor looks like a commander of hussars," the first impression upon a personal meeting was one of direct and winning good will and of genuine interest in the young person who stood before him (Heisenberg, *Naturwiss.*, Obit.).

In Born's opinion: Theoretical physics is a subject which attracts youngsters with a philosophic mind who speculate about the highest principles without sufficient foundations. just this type Sommerfeld knew how to handle, leading them to recognize their lack of knowledge, training them by personal, informal instruction, taking an interest in them and having time to spare for them (RSO).

Sommerfeld very early gave his students actual questions of physics as problems and let them take part directly in the progress of physics by discussing in seminar letters from Einstein or Bohr, communicating new results or considerations (Heisenberg, *Naturwiss*., Obit.).

Sommerfeld's method was personal instruction, like tutoring at the British universities, but less methodical and formal. Often before or after the Colloquium Sommerfeld was seen at the Hofgarten-Café discussing problems with some collaborators and covering the marble tables with formulae (Born, RSO).

Sommerfeld: "Sie sollen sich nicht darum kümmem, ob das Integral konvergiert, Sie sollen es ausrechnen!" [Scherzer, *Phys. Blätter* 7 (1951): p. 222].

Sommerfeld's willingness to display his ignorance: "I [Morse] often remembered him saying to someone (myself at times!), 'I'm sorry, can you explain this more fully? I don't grasp these ideas quickly!"', [Kirkpatrick, *Amer.* *J. Phys.* 17 (1949): p. 222.]

Sommerfeld took care that the power of his students was correctly applied and not frittered away. Sommerfeld had forbidden Heisenberg, as a beginning physicist, to play chess (Heisenberg, *Naturwiss*., Obit.).

Sommerfeld favored (for his students) every recreation from intellectual work, whether a walk in the English Garden or a trip to the mountains (Heisenberg, *Naturwiss*., Obit.).

Sommerfeld had a ski hut in the Sudelfeld together with his mechanic Selmayr. J. Zenneck from the Technische Hochschule had the neighboring hut, and both he and Sommerfeld spent many weekends there with their doctoral candidates. Selmayr praised the good humor of American students-willingness to split wood, wash dishes [Sommerfeld, *Amer. J. Phys.* 17 (1949): p. 315].

Sommerfeld's activity as a teacher has left behind an almost greater effect than his great success as researcher (Heisenberg, *Naturwiss*., Obit.).

FRANCK, JAMES

1882. August 26. Franck was born in Hamburg, Germany. (Hea [N. H. Heathcote, *Nobel Prize* *Winners in Physics*, 1901-1950 (N.Y., 1953)], p. 229) (P-6). Jewish, his parents were Jacob and Rebecca (Drucker) (JWS [*Jews in the World of* *Science*] 1956).

He studied at the Wilhelm Gymnasium Hamburg (Hea, p. 229). "According to his own testimony, he was anything but a brilliant scholar" [Peter Pringsheim, "James Franck: In Honor of his 70th Birthday, August 26, 1952," *Rev. Mod.* *Phys.* 24 (1952) : pp. 117-119].

1901-02. Franck spent two semesters at the U. of Heidelberg where chemistry was his first study (Hea, p. 229; AMS [*American Men of Science*], 1960). Franck and Born first met here.

Went to U. of Berlin where he studied physics under E. Warburg and P. Drude (Hea, p. 229).

1906. Obtained his doctor's degree, student of E. Warburg (Hea, p. 229; AMS 1960; P-6). His thesis was on the motion of the charge-carrier in point discharges. Such themes were extremely popular in those days, since they were meant to clarify the atomic and molecular structure of matter [Kroebel, Werner, "Zum 70. Geburtstag von James Franck," *Naturwiss.,* 39 (1952): pp. 385-388; henceforth referred to as Kroebel].

For a short period Franck, was Assistant at Frankfurt-am-Main (Hea 229, AMS 1960), then Asst., Physics Lab., to Prof. Rubens at Berlin (Hea, p. 229; AMS 1960).

1907. On December 23 Franck married Ingrid Josephson. They had two daughters, Dagrnar (now Mrs. von Hippel) and Elizabeth (now Mrs. Lisco) (JWS 1956).

1908. Pringsheim met Franck at the Institute, Berlin U., and the acquaintance grew into a solid friendship (Pringsheim, p. 117).

1911-16. Privatdozent, Berlin U. (AMS 1960).

In those years he was associated with such scientists as Pringsheim, R. W. Wood, A. Wehnelt, R. W. Pohl and L. Meitner, with whom he developed a solid friendship (Kroebel).

Around 1913. According to Kroebel, Franck became an associate of Hertz, with whom he continued the "original" problem of investigating the structure of atoms and molecules and their elementary processes, in connection with ionization potential and the quantum hypothesis. He depended upon his own varied earlier work on the motion of ions in various gases as well as on spectroscopic investigations, especially one carried out with R. W. Wood about the connection between the quantum hypothesis and potential of ionization. His own "strong empirical-intuitive" qualities were of great help in his researches, especially the decisive discoveries of 1913-1914, which won Franck and Hertz the Nobel Prize. These discoveries were the first experimental confirmation of the then hypothetical quantum theory and the Bohr atomic model (Kroebel). [The article with Wood appears to have been published in *Phil. Mag.* 21 (1911).]

The famous Franck-Hertz experiment (Pringsheim, p. 118).

It was a modification of Lenard's method that Franck and Hertz used in their researches on electron impact, the purpose of which was to investigate the cha ges of energy within the atom by direct measurement of the quantity of energy transferred to the atom in an electric collision. They took full advantage of the improvements in vacuum-pump technique made since Lenard's experiments. [Their results] . . . provided direct experimental proof of the fundamental assumption of Bohr's theory of the atom (which had appeared some six months before the completion of these researches) (Hea, pp. 230-247).

At the outbreak of the war, Franck made discoveries regarding the electrical excitation of gases, which added greatly to the world's understanding of atomic matter (A. H. Compton, *Atomic Quest: A Personal* *Narrative, p.* 121).

1914. Franck was sent to the front as a private (Pringsheim, 117). He served with the German Army and was decorated with the Iron Cross (Cbg). He emerged as a captain "no small distinction in a country in which military leadership was usually the privilege of a specially trained and honored class" (Compton, *Quest,* p. 121).

1916. Franck was promoted to the rank of lieutenant but "was recalled to do more useful work at home" (Pringsheim, p. 117).

1916-18. Assoc. Prof., physics, Berlin U. (AMS 1960).

1917-18. Assoc. Prof., physics, Berlin U. (AMS 1960).

1918-20. At the end of the World War he became a member and head of one of the departments of the Kaiser-Wilhelm Institute of Physical Chemistry at Berlin-Dahlem, which was then under the direction of Fritz Haber (winner of the 1918 Nobel Prize in chemistry) (Hea, p. 229) (P-6) (AMS 1960).

1920-33. Professor of Exper. Physics at Göttingen and Dir. of the II. Physical Institute (Hea, pp. 229-230) (P-5) (AMS 1960).

It was completely denuded of equipment. From his own private resources he supplied apparatus . . . this lab. became a center for the education not only of young German scientists, but, more than perhaps any other place in Europe, it became the favorite gathering point also for young U. S. physicists and chemists (Compton, *Quest,* pp. 121-122).

These years "were the most brilliant of his academic career. Franck's institute became one of the most important centers of research in atomic and molecular physics . . . His name attracted advanced scientists from abroad. . ." (Pringsheim, p. 117).

Post World War I. He was extremely popular as a teacher and he selected the very best men among the applicants to his Institute from both Germany and abroad. Among these students of Franck were Blackett, Cario, Atkinson, Hanle, Herzberg, von Hippel, Houtermans, Kopfermann, Kroebel, Kuhn, Lochte-Holtgreven, Maier-Leibnitz, Mannkopff, Oldenberg, Rabinowitch, Rathenau, Sommermeyer, and Sponer. Moreover, because of his world renown, he had as visiting professors at Göttingen the following scientists: K. T. Compton, Condon, Duffendack, Kondratjew, Loomis, Joseph Mayer, Scheibe, Turner, Wieland, and Winans.

Scientific life at the Institute was usually active and was in close- contact with the latest research in atomic physics, especially in England and the USA (Kroebel).

"In the Göttingen period . . . fluorescence of gases and vapors , became the main object of Franck's research" (Pringsheim, p. 118).

Franck published in the *Zs. f. Phys.* about 70 of his own research projects and about 70 papers by his students and collaborators. These papers dealt with the elucidation of the elementary processes of atomic and elementary molecular structure. Some of them dealt with the discovery of collisions of the first and second kind; some, with the transference of excitation energy into translation energy, and *vice versa,* resulting among other things in the interpretation of the continua in the spectra of atoms and molecules, and the important determination of energy of dissociation. Franck also contributed to the clarification of the type of binding in homo-polar and hetero-polar molecules as well as to the understanding of predissociation and the Franck-Condon principle (Kroebel).

1924-25. Blackett worked at Göttingen with James Franck (Nobel).

1925. When Born had read Louis de Broglie's thesis he discussed it with his students and with James Franck, his colleague at Göttingen. When, as a result of the experiments of Davisson, Elsasser, one of Born's students, proposed to study the interference of de Broilie's waves by means of the diffraction of free electrons, Franck immediately replied: "It would be nice, but not necessary, since the experiments of Davisson and Germer sufficiently prove the existence of the effect" [*Louis de Broglie* (Paris, Alban Michel, 1953), pp. 165-166].

1926. Davisson attended the meeting of the British Association, for the Advancement of Science at Oxford. He took with him some curves relating to the single crystal. He showed them to Born, Hartree, and possibly Blackett. Born called in another continental physicist (possibly Franck) to view them. There was much discussion about them [Darrow, K.. K., "The Scientific Work of C. J. Davisson," *Bell Syst. Tech.* 130 (1951): p. 786].

Franck and Hertz were awarded the Nobel Prize in Physics "for their discovery of the laws governing the impact between an electron and an atom" (Hea, p. 229).

Autumn: Karl Compton was at Göttingen where students formed a torchlight procession as a celebration for Franck's Nobel Prize and the faculty showered him with congratulations (Compton, *Quest,* p. 122).

E. U. Condon's Ph.D. Dissertation (1926) was entitled: "On the Theory of Intensity Distribution in Band Systems." As Condon states in his thesis: "My work is merely an extension of a leading thought on this subject by Professor J. Franck."

Franck published *Anregung von Quantenspriingen durch stösse,* with P. Jordan.

1927. Franck was present at Oppenheimer's oral Ph.D. examination. Oppenheimer quoted as saying, "I got out of there just in time. He was beginning to ask me questions" (Shepley, J. R., *The Hydrogen Bomb* [N.Y., 1954], p. 33).

1928. Hon. LL.D., California (AMS1960).

1930. Born published a joint paper with James Franck (P-6).

Von Laue and Ladenburg were invited to visit physics institutes in the USA by the Rockefeller Foundation, for the purpose of planning a "German Institute" in the hope of reactivating the K. W. I. for Physics (RSO). The report delivered by von Laue and Ladenburg led to the decision to establish the physical plant for the K.W.I. with J. Franck as Director of the experimental part and von Laue as Director of the theoretical section (von Laue biog.).

1933. Shortly after Hitler came to power Franck, although exempt at first from the Nürnberg laws because of his war record, "resigned his professorship in protest against the Nazi racial laws" (CBg [Current Biography] 1957). Owing to Nazi policy, Franck left Germany (von Laue biog.).

To Franck, Hitler's attitude toward science was as evil as his attitude toward the Jews, for science was to be of distinctive value to the German nation only. Franck published in the public press strongly-worded statements defending the support of pure science (Compton, *Quest*, pp. 122-23).

1933-34. Temporary job at Mass. Inst. Tech. (Compton, *Quest*, p. 123).
Speyer Prof., Johns Hopkins U. (AMS 1960). 1934-35. Guest Prof., U. Copenhagen (P-7a). .1935-38. Prof., Johns Hopkins U. (AMS 160).

1938-47. Prof. of physical chemistry, U. Chicago (Hea, 230).

1941. Hitchcock Prof., Berkeley (JWS 1956). 1942. His first wife died (CBg 1957).

1942-43. Director, Div. of Chemistry, Metallurgical labs., U. Chicago (JWS 1956).

1943-45. Assoc. Director, Div. of Chemistry, U. Chicago (JWS 1956).

1945. Franck "became the initiator of a drive to warn the American leaders of the implications of the new weapon" (*Saturday Review*, Aug. 4, 1956). During World War II he was the chairman of the Chemical Lab. and the Atomic Bomb project at Chicago, dealing with the chemical separation process for plutonium (Kroebel).

1946. Married, for the second time, Hertha Sponer (JWS 1956).

Visiting Prof., Iowa State Coll. (JWS 1956).

1947. Prof. Emeritus, U. Chicago (P-7a).

1949-56. Chairman, Research Group on Photosynthesis, Institute of Radiobiology and Biophysics, U. Chicago (JWS 1956; AMS 1960).

1951. Max Planck Medal (P-7a).

1954. Dr. h.c., Hebr. Inst. Technology, Haifa (P-7a).

J. Franck, as a member of an advisory panel for the Fed. of Amer. Scientists, came out for Oppenheimer (Oppenheimer biog.).

1955. Rumford Medal. (P-7a).

1957. Hon. Dr. rer. nat., Heidelberg (AMS 1960).

1958. Dept. of Physics, Duke U. (WWA [*Who's Who in America*] 1960). This is one place of residence, where his wife Hertha Sponer Franck is a professor; AMS 1960 gives the address as Dept. of Chemistry, U. Chicago.

*Personal Data*

Interests: Molecular and atomic physics (AMS 1960). Photosynthesis and physical background of photochemistry (AMS 1960).

Traits: "His obsession with science" and his "kindness, generosity and lovability" (Pringsheim, p. 119).

During his whole career Franck's experimental methods were characterized by a great simplicity in the apparatus he used . . . the same applied in "a certain respect to his theoretical reasoning; very little math, if any; a good deal of common sense and straight logic and most of all -- an indefatigable intensity.... He likes to talk about it with his students, with his co-workers, with anybody, but less in order to persuade them than to clarify the problems for himself" (Pringsheim, pp. 117-118).

Ehrenfest found Franck, Einstein, Planck and Bohr "refreshing" in a human way, in contrast to others who irritated him, some because of their aggression and others because of their pompousness (Bohr-Ehrenfest correspondence in the unpublished manuscript by M. J. Kleift, p. 24).