James Franck, 1882-1964 - Royal Societyrsbm.royalsocietypublishing.org/content/roybiogmem/11/53.full.pdf · JAMES FRANCK 1882-1964 ... It was at Heidelberg in 1901 or 1902 that he

James Franck, 1882-1964

H. G. Kuhn

1965, 53-74, published 1 November111965 Biogr. Mems Fell. R. Soc.

Email alerting service

herecorner of the article or click this article - sign up in the box at the top right-hand Receive free email alerts when new articles cite

http://rsbm.royalsocietypublishing.org/subscriptions, go to: Biogr. Mems Fell. R. Soc.To subscribe to

on May 24, 2018http://rsbm.royalsocietypublishing.org/Downloaded from on May 24, 2018http://rsbm.royalsocietypublishing.org/Downloaded from

http://rsbm.royalsocietypublishing.org//cgi/alerts/ctalert

http://rsbm.royalsocietypublishing.org/subscriptions

http://rsbm.royalsocietypublishing.org/


J”v - C •Owwô

on May 24, 2018http://rsbm.royalsocietypublishing.org/Downloaded from


JAM ES FRANCK

1882-1964

J ames Franck was born in Hamburg on 26 August 1882, the son of Jacob and Rebecca Franck. In his school, a sound training in classics was regarded as the principal aim of education, and it was largely due to Franck’s lack of interest in languages that he was considered to be a boy of little promise. At an early age he earned for himself the reputation of a dreamer on account of his tendency to become entirely absorbed in the observation of things around him, and in attempts to understand them. One day, during the Greek lesson, he discovered a grease spot in his note book, and noticed that he could see the writing on the other side of the page through the spot. This set him thinking until he had solved the scattering problem to his satisfaction, but left him a little behind the class in the matter of Greek verbs. A sharp thrust from the master, which caught him once again unprepared, demonstrated that classical studies were not to be his metier. According to his own report, he only just managed to pass the ‘Abiturium’ which enabled him to enrol at a university. His father, a Hamburg banker, sent him to Heidelberg to study law and economics, the normal preparation for a life o f‘affairs’ in those days; the parents hoped that he would later join the family firm.

James Franck had never any doubt that it was physics he wanted to study, but he dutifully attended lectures on law and economics. At the same time, however, he mixed with scientists and went to courses in geology and chemistry; the lectures on physics in Heidelberg—Lenard was not there at that time—were rather uninspiring. They reflected the widely held view that nothing fundamental in the subject remained to be discovered, since everything would ultimately be reduced to Newton’s mechanics.

It was at Heidelberg in 1901 or 1902 that he first met Max Born, and this meeting led to a friendship which was to last until Franck’s death, and to become of profound importance in the lives and the scientific work of both. Born writes: ‘Looking back to the Heidelberg semester, it appears to me that neither the professors nor the romantic atmosphere of that ancient university town were the important things in my life, but the friendship with James Franck.’ Born and other friends supported Franck in his rebellious scientific inclinations and in the efforts to persuade his parents to agree to a change in the course of his studies. It was due to their support as well as to Franck’s stubborn insistence that the parents finally gave in and allowed him to pursue the study of science. The remainder of the semester must have been a happy time, with the study of chemistry, geological excursions, and the



enjoyment of academic freedom. His way of getting absorbed in a task and his unperturbable good nature made him a favourite target of practical jokes. His friends, when asked to put his geological finds in the rucksack on his back, used to add rubbish and old bottles. He always enjoyed such jokes as much as any of the others.

54 Biographical Memoirs

BerlinFranck now wanted to devote himself seriously to physics and this is why,

in 1902, he went to Berlin, at that time the centre of physics in Germany. The professors there were Rubens, Emil Warburg and Planck, later also Drude and Einstein. Young physicists who later made their names, and with whom he kept in touch at various stages of his life were R. W. Wood, E. Meyer, E. Regener, A. Wehnelt, R. Pohl and W. Westphal. He formed lasting friendships with Otto Hahn, Lise Meitner and Peter Pringsheim. In those days physics offered no easy rewards or careers, and those who took it up were devoted to it and enthusiastic.

In the period up to the First World War, the regular colloquium in Berlin must have been an enormously stimulating and valuable experience for all the young physicists, and Franck speaks of it as the most important thing in his life. Some of the greatest men in physics, including visitors from all over the world, discussed the formidable problems presented by the discoveries in atomic physics and Planck’s quantum hypothesis. The informality and intellectual honesty of the discussions made a great impression on Franck. He describes how Planck, the great classical physicist, struggled against the revolutionary consequences of his own discoveries, trying hard to preserve as much as possible of the structure of classical concepts, and finally coming to the conviction that quantum concepts would enter all branches of physics. The younger generation took a lively part in these discussions, and Franck mentions specially F. A. Lindemann who was working with Nernst from 1908 to 1910, and describes him as intense and ‘exceedingly quick in the colloquium, especially in astronomy. He knew all the distances, made quick calculations in his head and was able to say: this and that must be wrong because . .

Franck entered the laboratory of Warburg who was later succeeded by Drude. Warburg suggested the study of corona discharges as a subject for his thesis. It was a time when much attention was devoted to gas discharges, with the aim of gaining an understanding of elementary processes involving electrons, atoms, molecules and ions. Townsend had published his measurements and theories on ionization, and Lenard had carried out his experiments on the scattering of electrons by atoms which led to his theory of idynamides\ the forerunner of Rutherford’s model of the atom. J. J. Thomson’s book on gas discharges was regarded as the bible in this field and was of great influence.

Franck found the study of corona discharges unrewarding; he soon formed the view that gas discharges were too complicated and that one should try to



James Franck 5^study the kinetics of electrons and ions undei simpler conditions. He changed the topic of his thesis and measured mobilities of ions by Rutherford’s method. For this work he received the Dr. Phil, in 1906. These and further experiments had demonstrated the smallness of the forces between electrons and some atoms such as those of the noble gases, in contrast to the ‘ affinity of electronegative atoms and of molecules. He now tried to find a connexion between these facts and the process of ionization by electron impact. In contrast to Townsend he assumed that elastic or partially elastic collisions could allow electrons to accumulate momentum over distances of many mean free paths. The concept of ionization potential had been coined by Stark, Lenard and J. J. Thomson. Lenard found its value generally to be 11 eV, evidently due to the presence of mercury vapour. He left it open whether this was the ionization potential valid for all gases or whether the same impurity was responsible for the results. Many physicists certainly expected at that time that ionization potentials were characteristic properties of atoms and molecules and it was generally taken for granted that light emission was conditional on ionization.

When Franck was joined by his younger colleague and friend Gustav Hertz, their collaboration resulted in a thorough, quantitative study of clastic collisions between electrons and atoms. The accumulation of kinetic energy over many free paths of the electrons in noble gases was definitely proved by their work. Substitution of mercury for the noble gases led to the well-known discovery of excitation potentials in 1914.

The experiments of Franck and Hertz gave the following clear-cut and clearly stated results:

(1) collisions of electrons with mercury atoms are perfectly elastic for electron energies up to 4-9 eV;

(2) above this limit, energy is transferred to the atom, but always in a quantum of 4*9 eV, while any excess is retained as kinetic energy;

(3) the inelastic collisions lead to emission of light of the resonance line 2537 A of mercury, and this line only; and the energy loss of the electron is equal to the quantum energy hv of this line.

Franck and Hertz fully realized the importance of their discovery which demonstrated the quantized energy transfer from kinetic to light energy. Einstein’s interpretation of the photo-electric effect had implied the quantized conversion of light energy into kinetic and potential energy, but it was based on very scanty experimental evidence at that time. Far more clearly and directly than the photoelectric effect, the experiments of Franck and Hertz proved the reality of the energy quanta postulated by Planck and provided a new method of measuring Planck’s constant.

To the reader of today it comes as a surprise to find that in their original papers and even as late as 1916, Franck and Hertz assume that the transfer of this energy quantum also causes ionization of the mercury atom, at least in some of the collisions, so that 4 • 9 volts is actually described as the ionization



r 6 Biographical Memoirs

potential of the mercury atom. A closer study of the background, however, makes these assumptions much less surprising.

Niels Bohr’s fundamental paper on the quantum theory of the hydrogen atom had been published about 6 months before the completion of their experiments, and Franck and Hertz had either not seen it at all or at any rate not realized its importance and its bearing on their experiments. An attitude of scepticism towards Bohr’s theory was widespread at that time. Sommerfeld is said to have regarded it at first as an ingenious mathematical formulation, but to have doubted whether it had any bearing on problems of atomic structure; J. J. Thomson did not think much of the theory. Two younger German physicists, both of them later Nobel Laureates, were reported to have sworn that they would give up physics if this ‘Bohr nonsense’ should turn out to be true.

On the experimental side, reliable observers had reported that mercury vapour was ionized when irradiated with light of the resonance line 2537 A, and Franck and Hertz themselves had observed some ionization. Several years were to elapse before these observations were shown to be caused by secondary effects; they were due partly to photoelectric effects on the electrodes and partly to metastable atoms being either ionized by further collisions or releasing electrons from the metal surfaces.

Though Bohr’s papers make it clear that the ionization energy of hydrogen is higher than the value hv of any spectral line, it was not so obvious that this would also hold for atoms wdth several electrons. Also, in the first papers in 1913, Bohr thinks of the emission of light as resulting from recombination of ions and electrons followed by cascade emission, not from direct excitation.

Before the acceptance of Bohr’s theory, it w as not at all clear how quantum concepts could be related to ionization phenomena, though Stark had put forward some ideas tending in the right direction. One thought of electrons in atoms and molecules largely in terms of harmonic oscillators, and it w7as reasonable to assume that the absorption of a quantum of energy would make it easier for an atom or molecule to be ionized. Franck & Westphal (1912) had looked for such an effect and had, in fact, found that irradiation of iodine vapour by strong light reduced the ionization potential. Though the observations were undoubtedly correct, their interpretation was more complicated and became possible only much later, on the basis of Franck’s work on the direct photo-dissociation of molecules.

The outbreak of the First World War, interrupting scientific work and the exchange of information, prolonged the state of confusion over the question of ionization. It was during the war that van der Bijl, on suggestions by Niels Bohr, proved the spurious nature of the photo-ionization effects mentioned.

In the concluding passages of his Nobel Lecture (1927), Franck speaks of ‘the wrong tracks and detours we took in a field where the straight road has now been opened up by Bohr’s theory’. This passage characterizes the relations which had developed in the meantime between Franck and Niels



Bohr. Max Born found that Franck regarded Bohr as almost infallible and recalls an occasion when he, Born, had cleared up a theoretical point for Franck by an explanation which could easily be tested by experiment. When he asked Franck a little later if he had tried the experiment, the answer was: ‘No, I am still waiting for a letter from Bohr.’

The time in Berlin, from 1902 to 1921, was important not only for Franck’s development as a physicist but also in his personal life. In 1911 he married Ingrid Josephson, a Swedish pianist from Goteborg, and their two daughters Dagmar and Lisa were born there.

From his own reports and those of his friends, one gains the impression of a rich and active life, a large circle of friends passionately devoted to physics and spending unlimited hours in the laboratory with experiments and discussions. The friendships merged into the home life, and we hear of musical evenings in the home of the Francks, with Einstein playing the violin and Lise Meitner introducing them to Brahms’s Lieder.

In 1911 Franck received the ‘venia legendi’, the first step in the career of a university teacher, in 1916 he was made an assistant professor and in 1918 associate professor.

The outbreak of war in 1914 interrupted the work of Franck and Hertz at a most critical stage; both joined up and were sent to the front. Though Franck received a commission and distinguished himself in the war, it was from a sense of duty rather than from conviction that he became a soldier, and the military atmosphere can never have been much to his liking. Born tells a story of Franck when he was first put in charge of a column of men; his words of command were ‘stand to attention!—please’ (Stillgestanden!— bitte). Commanding and bossing people about has always remained utterly against his nature, and the story, whether true or not, describes him well. His war service did not last very long; he caught dysentery in Russia, became severely ill and was sent home to recover.

From 1917 to 1921 Franck was head of a section of the Kaiser Wilhelm Institut f. Physikalische Chemie—later called Max Planck Institut—whose director was Fritz Haber. It was in these years that he met Niels Bohr for the first time. This first contact appears to have been during Bohr’s visit to Berlin when the younger physicists insisted on arranging a discussion meeting when they could have Bohr all to themselves, any full professor or Geheimrat being strictly excluded. They could ask him questions without inhibition, and Franck describes Bohr’s immense ability to concentrate, in the presence of others, while his face looked completely empty, until the answer was produced. In these talks, Bohr always stressed the provisional nature and philosophical inconsistency of his quantum theory. It was this wisdom and his complete freedom from conceit which created such deep respect and admiration in the young physicists that Franck describes it as bordering on hero worship. He also visited Niels Bohr in Copenhagen and established a lasting personal friendship with him.

Jointly with a number of co-workers Franck continued the study of the

James Franck 57



inelastic collisions of electrons with both atoms and molecules, of excitation- and ionization-potentials, but now with Bohr’s theory as a guiding principle. The theoretical adviser of the group was Fritz Reiche, and it was Franck, Knipping and Reiche who coined the word ''metastable ’ and established the important part of metastable states in excitation processes. The question of how metastable atoms finally lose their energy, now strongly occupied Franck’s attention. Franck & Grotrian (1921) show how the long life of metastable helium atoms could lead to formation of He2 molecules in discharges. Altogether, the formation of molecules interested him to an increasing extent, e.g. the formation and spectra of Hg2 and Na2.

GottingenIn 1921 Franck accepted the offer of a chair of experimental physics at

Gottingen. Max Born had been offered the chair of theoretical physics at that university, and he made his acceptance conditional on an offer of an experimental professorship to be made to Franck. The position was ideally suited to Franck; there were two professorships, each with its own department, though these were in the same building. One was occupied by R. Pohl who had the duty of giving the general lecture in physics, the ‘grosse Vorlesung’ which was the normal commitment of a full professor in Germany. It was attended by large numbers of students from all branches of science and was therefore very lucrative. Pohl, an excellent experimenter and lecturer, made a great success of these lectures, delivered in an almost popular style and with brilliant demonstrations. Franck disliked lecturing to large audiences and was glad not to be burdened with this task in Gottingen. Some years later, when he had the offer to become Rubens’s successor in Berlin, one of his conditions was that he would not have to give the large lecture. Though this was granted, he finally did not accept the offer.

Practical classes were the responsibility of Franck and his ‘Assistenten’ in Gottingen, and he often made an appearance there, talking to individual students about their experiment and discussing questions connected with it. This personal contact with the head of the Department was greatly valued by many students, even though it was bound to be a rare experience for any one of them.

Most important, Franck now found himself again in the same place with Max Born, and the close co-operation, friendship and exchange of ideas between these two are vividly remembered by anyone who had the good fortune to be at Gottingen at that time. The department of theoretical physics occupied a few rooms in the same building, and the close scientific and personal relations between the two professors included lecturers and research students. According to Born, he and Franck discussed every one of their publications together, in these 12 years, though they published no more than three papers together.

A regular feature was the seminar which Born and Franck held jointly. A student in his last year before the beginning of research, or a research student




would be given a subject on which he had to give a talk at the seminar, and had to stand up to friendly though quite searching questions. At that time, there was no university examination before the Dr.Phil, for a physicist, and the acceptance of a research student was left entirely in the hands of the professor. Admission to Franck’s laboratory became very competitive, and his decision was mainly based on the performance of the student at these seminars.

Once admitted, the research student became not only a pupil of Franck but a member of a community tied together by common scientific interests, friendship and, not least, by a feeling of respect and devotion to Franck. Fie himself would generally propose the subject of research for the student, but the progress of the work was supervised by him jointly with his ‘Assistenten’. Twice a week, at a fixed time, they all would tioop into the room of the student on a kind of ward-round to discuss progress, difficulties and questions of apparatus. Prolonged discussions with research students and especially with the members of the staff would take place either in his room or he would take one for a walk into the pleasant surroundings of Gottingen. On such occasions he would talk about his ideas and plans of research, clearing them up for himself while explaining them to the younger colleague and answering his questions. Such walks were a highly valued and unforgettable experience, and their only drawback was Franck’s fondness of warmth that tended to make him choose the sunniest paths. He would be too absorbed in the subject of the discussion to notice the discomfort of the young man at his side mopping his brow.

Life in the laboratory was characterized by great informality, allowing physics and private life to merge pleasantly into one another. At lunch time, the Professor and his Assistenten would bicycle home together or, in the summer, meet for a sandwich lunch in the open swimming pool. How extraordinary and unusual all this was can only be realized by those who knew the position of absolute power of professors in pre-war Germany and the stiffness and formality of their relations to the staff and students in most laboratories.

The weekly colloquium was held jointly by the three physics professors, Born, Franck and Pohl and was, not by compulsion but as a matter of course, attended by all members of the laboratory. These included always some foreign guests spending a semester or two in Gottingen. Among them were P. M. S. Blackett, R. d’E. Atkinson, E. G. Dymorvd, G. E. Gibson, R. B. Brode, L. A. Turner, F. W. Loomis, J. G. Winans, V. Kondratjew in Franck’s department, and P. Dirac, E. U. Condon, J. R. Oppenheimer and J. E. Lennard-Jones in Born’s department. The members of the staff and the research students naturally changed, but the following were in Franck’s laboratory at one time or another: O. Oldenberg, Hertha Sponer, H. Kopfermann, G. Cario, A. v. Hippel, W. Hanle, F. G. Houtermans, G. Herzberg, R. Mannkopff, H. G. Kuhn, W. Kroebel, W. Lochte-Holtgreven, H. Maier-Leibnitz, E. Rabinowitch. Co-workers of Born included F. Hund,

James Franck 59



uiu.§ £uio;u psqoxs uu q;iM uoisiqoo uo ‘pjnoo uojpsp mojs u isjqissod sq osju ;smu ssssojd ssjsaui sq; s;sudun uoj;osp Aq ps;pxs 3q pjnos srao)B jj

•USSnpiOQ ;U ;SSJS;UI JO ppg Siq 0;UI JS;US p0llUdl{0 pUU‘uoijvpossip jpq; puu sdpnodpm jo uoi imcnpq £jsas

-Moq £sjoui put? 3jojy ' (jsSuudg : uqjsq ‘9261) 9SSQIS llomV uoa ‘BuriSdxuy qooq siq ui qsuujjj Aq £uupjof j q;iM diqsjoq;nu-os ui ‘psMstASj ussq suq puu us§up;o£) ui ;ssjs;ui siq pjoq o; psnupuos ;osfqns siqx jpsq ;ss§Sns pjnoM siuo;v yjtm suoxpdp fo suopipoo sqq Suupsuios ‘uqjsg ui A;iApsu s^suujj; Suizijuuuuus ssujqd ;joqs u pug o; psu; suo jj

•sjsq ps;duis;;u sq uus s;ssjs;ui puu qjoA\ uiuui stqsuujj[ jo suq;no jsijq u uuq; sjoui oj\j *suopssS§ns puu sspvpu siq uiojj ps;gsusq oqM sjsq;o q;iM suoissnssip ui ps;sisuoo A;iApsu siq jo qsmu osfy ‘qjoM sq; psspvisdns ApSjuj puu ps;upiui 3q qSnoq; £s;upqjuuo sq; jo ;uq; o; psppu §upq suiuu siq ;noq;iM psqsqqnd AqujsusS sjsm ssssq; csjo;soq jo s;us;uos sq; ssnussq spm§ Auu Apsjuss si suopusqqnd siq jo ;sq sqjy 'us§up;ofj ui sjusA 21 siq Suunp ssisAqd uo ssusngui siqpUU qjOM S^SUUjg UO ;jodsJ SAISUSqSjdlUOS U 3AI§ OJ qusqjip 3q pjUOM }J

’UOlSSSSOjdqsjo; b jo uijoj sq; ui qsuujg o; s;nqu; jpq; piud A;isjsaiuu sq; jo s;uspn;s sq; puu £us§up;o0 ui Supiofsj ;usj§ sum sjsqx ’vesA ;uq; ui pspjUMU ussq ;ou puq qoiqM ^261 JOJ 9zIJd sq; sum ;i Jsjupus;od uopuqsxs jo AjsAOOSip juiof jpq; joj 3zijx pqo^q sqj pspjuMU sjsm zjsjj puu qouuj^ 9261 UI

{'S3SS330jd uoisiqoouiojj psuiuS Apjuuiijd sjsm sjoojd Aui JjU3J§ sum siq; ui sjuqs seqouuJX •psjdsoou AqujsusS mou msia u £33uds uopujnSguoo ui Aqsusp Aqgquqojd su j s</* | jo uopu;3jdj3;ui sq; o; suiuo snq; j ‘ssaum Aq pspinS Moqsuios sjsm puu psjsixs ssppjud qoiqM ui punoj sq o; puq 3JOj3j3q; j | spsSuipojqog jo Suiuusui sq; jo uopuuu|dxs jsq;ouy *3|qusu3dsipui sum ;d3ouoo sppjud sq; ;uq; sui psouiAuoo siq; Suiop ui sssoons ;usjS siq puu ssppjud jo sssssoojd uoisqpo SuisApuu jo ;ju qjsdns s^qouujj;, : siq; uo s;u3uiuioo ujoq •soiuuqosui uin;uunb jo s;d33uoo |u;u3uiupunj sq; jo suo suijoj mou qsiqM uojfvpxcfx3fm jvoippvjs siq pssodojd ujoq q;un Apjpus dn usai§ sq o; SAuq ppoM ;dssuos sppjud sq; ;uq; ;q§noq; Aqupiui jsSuipojqsg 'uopsunj saum s{j3Suipojqsq jo uopu;sjdjs;ui sq; si ujoq puu qsuujj[ ussM;sq suopupj sq; jo puu siq; jo sjduiuxs uu puu £;uu;joduu Apu^nopjud sum s;spisAqd {u; -usuiijsdxs puu pspuuisq;uui ussM;sq suspijo sSuuqsxs sq; £§uipuu;sjspun psisAqd pspsosjd us;jo uopupiujoj |uspuuisq;uui sq; usqM sun; u ;y •sspqusiuqss; pspuuisq;uui sq; puiqsq sppussss sq; dn Moqs o; uuppsjosq; sq; Suisjoj ui snpA ;usjS jo sq o; psAOjd us;jo qsuujj jo uopusAJs;ui puu ssusssjd sqx 'spoq;sui-snpAus§p puu -Jo;ujsdo £-xij;uui su qsns £s;spisAqd o; juqiuiuj ;sA ;ou ssuqdpsip |uspuuisq;um jo suijs; ui pssssjdxs puu ;suj;squ Ajsa sq o; ;pj us;jo sjsm lunmboqos sq; ;u suoissnssip puu sqp; juspsjosq; sq; ‘ssiuuqssui uin;uunb jo uopnjoAS sq; jo sAup sssq; uj

•s;s|duios uiojj juj sju s;sq q;oq ;nq £jsAup\[-;jsddso0 uuup\[ puu jdoqsspM ‘JS{;pH 'M ‘jauxqyVV ‘3 ‘uupjof ‘Sjsqusspjj ^

mouldj/\[ ivoii{4vxSoiq 09

on May 24, 2018 http://rsbm.royalsocietypublishing.org/ Downloaded from


kinetic energy at the expense of the excitation energy. Klein and Rosseland had pointed this out and suggested the name ‘ of the secondSince the process was difficult to observe in this form, Franck and his co-workers studied the de-excitation by collisions of the second kind with other atoms or with molecules. This could be done by measuring the extinction of fluorescence on addition of foreign gases. It was found that excitation energy could be converted not only into kinetic energy but even more effectively into other forms of energy. As early as 1911, Franck and Wood had found that the series of doublets in the resonance spectrum of iodine vapour was changed into the full band spectrum on admixture of gases, and this could now be explained as loss of vibrational and rotational energy as result of collisions of the second kind. The dissociation of hydrogen molecules by collisions with excited mercury atoms was discovered by Cario & Franck (1922) and has become a well-known example of sensitized photo-chemical reactions. Transfer of excitation energy from one atom to another was found by the same authors (1923) and has become known as sensitized :they found that in a mixture of mercury and thallium vapour, irradiation with mercury resonance light produced strong fluorescence of thallium atoms. Franck was the first to point out the importance of resonance in energy transfer of this kind. The great efficiency of the process of transfer of energy from mercury to thallium was correctly ascribed to the closeness of their excitation potentials, and the ease of transfer of mercury atoms from the level 6 to the metastable level 6 :iP0 was similarly explained. Franck (1928) also pointed out the possibility of a type of collision of the second kind which forms the inverse to the process of ionization by electron impact: the collision of a positive ion with two slow electrons can, by recombination, produce a neutral atom and a fast electron.

The state of polarization of fluorescent light was another subject of research in Gdttingen by Franck and his pupils. In particular, the depolarization caused by an external magnetic field, which formed the subject of Hanle’s dissertation, has proved to be of lasting importance. Quite recently, the '‘Hanle effect’ has been used for measurements of life times of excited states.

It was presumably the excitation of molecules by electron impact that led Franck to think about the connexion between electronic and vibrational energy, and it was here that the collaboration of Born & Franck proved most fruitful. Their two joint papers (1925) contain the basic ideas of molecule formation by triple collision, of the Franck-Condon principle, the theory of continuous molecular spectra, and of adsorption catalysis. Potential curves are used here in the now familiar way, and also the influence of rotation on these curves is discussed. The concept of ‘ quasi-molecules’ makes its first appearance and is defined in these papers. For example, the second of these states: ‘We therefore find that, with regard to emission and absorption of light, a pair of atoms during a collision behaves just as if they formed a genuine molecule with non- quantised oscillation and rotation.’

In Franck’s paper on ‘Elementary processes of photochemical reactions’

James Franck 61



(1925) the method of deriving energies of dissociation from extrapolation of vibrational levels and the principle governing the intensity distribution among vibrational transitions in electronic spectra (later ‘ ’)are stated for the first time. It is interesting to see how he formed this unified picture of the process mainly from three previously unconnected sources. Lenz, in his theory of band spectra, had pointed out that the correspondence principle leads to a connexion between the coupling strength of oscillatory and electronic motion, and the change of vibrational energy; Franck & Born had separated clearly the electronic motion and that of the nuclei. Mecke had observed a long series of vibrational transitions with markedly decreasing spacings in the spectrum of iodine. By linking up these facts and theories, Franck arrived at his clear, graphical statement of the connexion between electron transition and motion of the nuclei. Condon’s quantum-mechanical treatment added rigour and quantitative information to what is now known as the ''Franck-Condon principle’.

At the time of Franck’s paper (1925), the first excitation energies of the halogen atoms were not known, and he had to estimate them. When they were derived from the spectra soon afterwards, Franck’s predictions of the convergence limits in bromine and chlorine were confirmed by measurements in his laboratory, and the method now gave accurate values of the heat of dissociation of the halogen molecules. Observation of continuous absorption spectra and fluorescence experiments provided independent proof for the correctness of Franck’s postulate of photo-dissociation in a single process, without collisions.

Though Franck fully recognized the power of mathematical and quantum- mechanical methods and had a good understanding of their essentials, he always developed his ideas from concrete models and pictures. He used to discuss problems of molecular vibration by using his two fists as representing the nuclei and, of course, by means of innumerable potential curves of different shapes drawn on the blackboard.

In the following years, Franck’s method of extrapolation was applied to measurements and estimates of energies of dissociation, in his and many other laboratories. Numerous studies of band spectra, mainly in absorption and fluorescence, were carried out by him and his co-workers. In heteropolar molecules, such as alkali-halides in the vapour state, absorption maxima without structure were found and explained by direct photo-dissociation due to transitions to the repulsion branch of the potential curve above the dissociation limit. The state of the dissociation products could often be identified. Sequences of structureless bands were explained as transitions from vibrational levels of the molecule in the ground state to an excited state with no or hardly any minimum in the potential curve.

The possibility of following up the vibiational states to the limit of convergence led Franck to the attempt to define atomic and ionic bonds in diatomic molecules. He assumed that adiabatic increase of internucleai distance would lead in a unique way to either atomic or ionic states. Further




developments of the theory of molecular states later showed that this is not generally permissible.

The Franck-Condonprinciple has since been applied to such a number andvariety of phenomena in chemistry and molecular spectroscopy that it would be futile to quote individual examples. It has been extended to polyatomic molecules, to predissociation phenomena, to the study of Van der Waals molecules and to the pressure broadening of spectral lines.

The study of continuous bands in molecular vapours led Franck to the chemically more involved phenomena of absorption bands in liquids and eventually to his work on photosynthesis which became his main interest in later years.

In 1933 the fruitful and happy period in Gottingen was brought to an end by political events. When Hitler came to power the universities were to be ‘cleansed’ of all those who, by race or conviction, were objectionable to the new regime. Franck himself, though Jewish, could have remained in office because he had fought in the war, but the new legislation would have forced him to dismiss co-workers and students who were either ‘non-aryan’ or politically suspect. It would have been easy for Franck to compromise, and there were many good and reasonable arguments in favour of such a course; but Franck saw clearly that this was a fundamental issue, to be decided on principle instead of expedience. Against the warning of many genuinely well-meaning colleagues, he resigned his professorship in April 1933 and published his statement of resignation and protest in the national press. Neither he nor anyone else thought that this action would have any effect on the course of events, but it was simply the right thing to do and will be gratefully remembered by many as one of the few open protests coming from the universities in Germany against racial discrimination and the suppression of academic freedom. A considerable personal risk was clearly involved, but fortunately nothing happened to Franck, and later in the year he and his family left Germany.

Before leaving, however, Franck made it his task to use his connexions with foreign scientists for helping many young colleagues and pupils to find refuge abroad. In these years of world depression this was far from easy. The active and powerful help of his old friend F. A. Lindemann, later Lord Cherwell, was timely and highly welcome. Within less than a year the laboratory virtually dispersed; most of the staff members were either dismissed or had to leave the university or the country for one reason or another.

James Franck 63

AmericaAfter a short visit to Baltimore and other places in America Franck

spent more than a year in Copenhagen as visiting professor in Niels Bohr’s department. In 1935 he and his family finally moved to the U.S.A. where he accepted a professorship at Johns Hopkins University, Baltimore.

During these years of transition, his publications with E. Rabinowitch and



H. Levi deal with photochemical effects in solutions and the primary recombination of the dissociation products. His entry into the field of photosynthesis is marked by experimental work with R. W. Wood and theoretical work with K. F. Herzfeld.

In 1938 he was appointed Professor of Physical Chemistry at the Uni versity of Chicago where the Samuel Fels Foundation established a laboratory for photosynthesis. Until his retirement in 1949 he directed this laboratory, and after this time, when his co-worker and friend H. Gaffron had been made director, he continued to take an active part in the work of the laboratory.

Photosynthesis was not, however, his only interest while in Chicago, as the list of publications shows. His joint paper with E. Teller (1938) opened up the application of the exciton theory to photochemical changes in crystals and has proved to be of basic importance in this field. It has advanced the understanding of the photographic process. The paper with J. E. Mayer (1947) dealt with the transport of materials through cell membranes.

During the Second World War Franck decided to shelve his research and joined the Metallurgical Project in Chicago, which formed part of the atomic bomb project; he was put in charge of the chemistry division. The ultimate aim of this work was as distasteful to him as to most, but the danger that the bomb would first be made by Germany under Hitler was too real to be ignored. The surrender of Germany altered the situation and he, like many scientists involved in the project, became seriously concerned about the consequences of using this entirely new kind of weapon. The director of the Metallurgical Laboratory appointed a committee consisting of three physicists, three chemists and a biologist under the chairmanship of James Franck to consider the ‘social and political implications’ of using the bomb. The report, submitted to the Secretary for War on 11 June 1945, six days before the New' Mexico test, became known as the ‘ Franck ’ and was later released and published in the Bulletin of Atomic Scientists (1946). It urges the U.S. Government to consider the use of the bomb as a fateful political decision and not merely as a matter of military tactics. It points to the danger of a nuclear arms race and concludes: ‘If the United States were to be the first to release this new means of indiscriminate destruction upon mankind, she would sacrifice public support throughout the world, precipitate the race for armaments and prejudice the possibility of reaching an international agreement on the future control of such weapons. Much more favourable conditions for the eventual achievement of such an agreement could be created if nuclear bombs were first revealed to the world by a demonstration in an appropriately selected, uninhabited area.’

Whether one agrees with these conclusions or not, the Franck report will remain a historical document testifying to the sense of responsibility of the scientists engaged in the project. The dangers of nuclear war, the problem of East-West relations and all their political implications always remained a matter of deep concern for Franck. After the war Franck was not, I believe, on any of the committees advising the Administration, but many of the




scientists with such responsibilities kept in touch with him and sought his advice.

After Franck’s emigration, if not earlier, the health of his wife gradually deteriorated, and she died in 1942. It was fortunate for him that both his daughters, Dagmar v. Hippel and Lisa Lisco, had also settled in America. The close attachment to them and their families greatly added to the happiness of his life; his grandchildren were attached to him and always liked to discuss with him their problems, whether they were human or scientific.

In 1946 Franck married Hertha Sponer, professor at Duke University, and divided his time between Chicago and their home in Durham, North Carolina. She had been his pupil and co-worker and an old friend of himself and his family.

After the war, Franck resumed his work on photosynthesis. There has been much controversy on his theories, and it is difficult for the non-specialist to assess their importance and validity. What follows is the text, with small modifications, of a review written by Professor Eugene Rabinowitch.

’Having established many of the basic relationships determining the interaction between simple molecules and light quanta, Franck became interested, in 1933, in the fundamental photochemical process in nature, photosynthesis—the process by which simple stable molecules, C 0 2 and H20 , are converted, in living plant cells, into organic materials, primarily into carbohydrates (CH20)„. He hoped at first that application of quantitative, physical experimentation to this process, which had been studied since the late eighteenth century by plant physiologists and organic chemists, would soon clarify its most puzzling aspect, namely the mechanism by which a large proportion of the energy of several, probably eight, quanta of visible

light is converted into chemical energy of the system - (CH20 ) „ + 0 2. Then

problem proved, however, more difficult than he had expected and held him spellbound for the last 30 years of his life. His last paper, together with J . Rosenberg, summarizing his ideas about the mechanism of photosynthesis, was sent to the Journal of Theoretical Biology a few weeks before his death.

‘Until growing infirmity put an end to Franck’s work in Chicago, he carried out a considerable number of experimental investigations, particularly on the fluorescence of chlorophyll in the living cell, and these remain fundamental for any acceptable theory of photosynthesis. In agreement with earlier work by Wassink and others, Franck & Shiau (1947) found that very high intensity of illumination brought the yield of fluorescence of chlorophyll in vivo to about twice the level observed in weak light.

‘These and similar findings have led Franck to the development of a biochemical and biophysical model of photosynthesis. Even after he was obliged to stop his experimental work, five or six years ago, because of a series of heart attacks, he continued work on this model, trying to adapt it to cover new experimental results.

James Franck 65



‘Franck’s specific model of photosynthesis has not been generally accepted by other researchers in this field, particularly because for many of them the most important aspect of the problem was the detailed sequences of chemical transformations involved in the conversion of C 0 2 into sugar, and not the primary photochemical act in which light was converted into chemical energy, as for Franck. His work was, however, influential in that it gradually led the students of photosynthesis to recognize the importance of his theoretical points of view and physical findings, and try to do justice to them in their speculations. Recently the two developments, evolution of Franck’s model of photosynthesis and evolution of general understanding of the biophysical aspects of photosynthesis, led to a considerable rapprochement. At the Photosynthesis Conference in Airlie House, Virginia, in October 1963, Franck had the satisfaction of discussing his concepts with others who had full understanding for his approach. There remains one important difference between the model of Franck and Rosenberg and those derived by other workers: all assume two successive photochemical steps lifting hydrogen from its low reducing potential to its high reducing potential in CH20 ; but while others are inclined to see these two steps as occurring in two different chlorophyll molecules, Franck envisages a two-step process sensitized by one and the same chlorophyll molecule, first in the singlet and then in the triplet excited state. This concept is based on the above-mentioned doubling of the yield of fluorescence upon light saturation of photosynthesis. It may well be that Franck’s ingenious picture will prove to be the right one although it requires some ad hoc hypotheses to explain certain other experimental facts.

‘Franck’s controversy with Otto Warburg about the quantum yield of photosynthesis, which attracted so much attention, was a case of Franck standing up for the experimental results of Emerson and others which made sense to him as a physicist, and Warburg’s insistence that the conclusions of spectroscopy, reaction kinetics and thermodynamics, except for its first law, are of no validity for the living cell. According to Warburg, plants can carry out photosynthesis with a quantum yield requirement of less than three quanta per molecule C 0 2, which means 100% conversion of light energy into chemical energy. While Franck began with the difficulty of interpreting Warburg’s first findings of a quantum requirement of 4, and was much relieved when Emerson and others found considerably higher values, perhaps down to 6 but more likely 8 or more, Warburg reduced his figure to the completely implausible value of 2-7, making photosynthesis into a complex chemical mechanism operating without any friction. The reason for the experimental disagreement between Warburg and nearly all others who have measured the quantum requirement remains unexplained.’

A full discussion of Franck’s theoretical work on photosynthesis has most recently been given by Roderick & Clayton in their book on Molecular physics in photosynthesis (Blaisdell Publ. Co., New York & London, 1965).

The award of the Rumford Medal of the American Academy of Arts and




Sciences in 1955 for his work on photosynthesis showed the increasing recognition of the value of his work in this field. It was one of the numerous honours he received, apart from the Nobel Prize and memberships of Academies and learned societies.

He became a Foreign Member of the Royal Society in April 1964, only a few weeks before his death.

James Franck 67

Franck’s direct contributions to the fields of physics, chemistry and biology, during more than half a century of active life, are recorded in his publications and those of others acknowledging his advice. A contribution more elusive to the biographer though no less real and important was the influence of his personality on those who worked with him or under him. He always talked on equal terms, no matter how great the real difference in understanding might be, so that everyone felt at ease with him. He did this not by any intention but simply by always being his natural self, a self that was singularly free from conceit or false pretences. In such talks one could take part in his struggle with a problem and could see a confused situation gradually clear up. Dialogue or discussion in small groups were his form of expression, rather than lecturing. Even the specialized lectures to small audiences in Gottingen made him feel a little uncomfortable, and before these lectures one often met him wandering about the corridor, pensive and just a little nervous. Though one remembers his face mainly as serious and reposed, he loved jokes and could laugh heartily, but his humour was never caustic or at the expense of others.

Throughout his life, people came to Franck to ask his opinion and advice, not only in matters of science but in all kinds of difficult situations where he could claim no special knowledge or experience. This unlimited confidence, and the affection he inspired can be ascribed to two features which stood out in his character: his absolute, natural honesty, both intellectual and moral, and his profound human warmth and kindness. He would give his attention and thoughts to a human problem as thoroughly as to a scientific one.

His character was written on his face. No one who had the good fortune of having known him will ever forget the clear, warm look in his eyes. Nothing small or petty had any room in his thoughts or feelings.

The Hitler period had cast a deep and lasting shadow over Franck’s life, and it was not an easy decision for him to visit Germany again for the first time after the war. The welcome he found there not only among his old friends and pupils, but in a much wider circle, must have shown him how much had changed in Germany, and he repeated his visit several times. In 1951 he was awarded the Max Planck Medal of the German Physical Society, and in 1953 the town of Gottingen gave him the Freedom of the City, at the same time as Born and some other old friends of Franck’s. Heidelberg and other German universities awarded him honorary Doctor’s degrees.



68In the post-war years Franck’s health caused him increasing trouble and

gave concern to his family and friends. Fortunately, this physical decline had no effect whatsoever on his mind which remained clear and active to the last. He had just visited old friends in Germany and spent happy hours of reminiscing with them when death came rapidly and painlessly to him in Gottingen on 21 May 1964.

Acknowledgements and referencesMrs Hertha Sponer-Franck and the families von Hippel and Lisco kindly

helped me with suggestions and material, and I am greatly indebted to Professor Max Born, F.R.S., for his letters from which I was allowed to quote; to Professor Thomas S. Kuhn and Professor F. Hund for their advice and for enabling me to use the records taken by the Sources for history of quantum physics; also to Professor H. Gaffron and Professor O. R. Frisch, F.R.S.

I specially wish to record my thanks to Professor E. Rabinowitch for his contribution on the photosynthesis work, and to Professor R. L. Platzman for permission to use the bibliography which he has compiled.

I also used the following sources:P. Pringsheim, 1952, Rev. Mod. Phys. 24, 117.W. Kroebel, 1952, Naturwissenschaften, 39, 385.M. Born & W. Westphal, 1964, Physikal. Blaett. 20, 324.W. Kroebel, 1964, Naturwissenschaften, 51, 421.L. Meitner, 1964, Nature, Lond. 203, 916.E. Rabinowitch, 1964, Bull. Atom. Scient. p. 16.G. Hertz, 1964, Ann. Phys. Lpz. 15, 1.

H. G. K uhn

Biographical Memoirs

BIBLIOGRAPHY

Scientific papers1906. Uber die Beweglichkeit der Ladungstrager der Spitzenentladung. Verb. Phys. Ges.

Berlin, 8, 252-263.1906. Uber die Beweglichkeit der Ladungstrager der Spitzenentladung. Ann. Phys. Lpz.

21, 972-1000.1907. (With R. P o h l .) Eine Methode zur Bestimmung der Ionenbeweglichkeit in kleinen

Gasmengen. Verb. Phys. Ges. Berlin, 9, 69-75.1907. (With R. P o h l .) Die Ionenbeweglichkeit in Helium. Verb. Phys. Ges. Berlin, 9.

194-199.1908. (With R. P o h l .) Zur Frage nach der Geschwindigkeit der Rontgenstrahlen. Verb.

Phys. Ges. Berlin, 10, 117-136.1908. (With R. P o h l .) Zur Frage nach der Geschwindigkeit der Rontgenstrahlen II.

Verh. Phys. Ges. Berlin, 10, 489-494.1909. (With W. W estph a l .) Uber doppelt geladene Gasionen. Verb. Phys. Ges. Berlin, 11,

146-154.



1909. (With W. Westphal.) Uber die Ladung von Gasionen. Verh. Phys. , 11.276-280.

1909. Uber die Ionenbeweglichkeit der radioaktiven Restatome und die Masse des Gasions.Verh. Phys. Ges. Berlin, 11, 397-405.

1910. Uber die Ionenbeweglichkeit in Argon und den Einfluss geringer Mengen Sauerstoffsauf diese Grosse. Verh. Phys. Ges. Berlin, 12, 291-298.

1910. (With A. Wehnelt.) Uber Beziehungen zwischen Faradayschem Gesetz und Gasentladungen. Verh. Phys. Ges. Berlin, 12, 444-456.

1910. Uber das Vorkommen freier Elektronen in chemisch tragen Gasen bei Atmos-pharendruck. Verh. Phys. Ges. Berlin, 12, 613-620.

1911. (With R. W. Wood.) Uber die Beeinflussung der Fluoreszenz von Jod- und Queck-silberdampf durch Beimengung von Gasen mit verschiedener Affinitat zum Elektron. Verh. Phys. Ges. Berlin, 13, 78-83.

1911. (With R. W. Wood.) The influence upon the fluorescence of iodine and mercury of gases with different affinities for electrons. Phil. Mag. 21, 314-318.

1911. (With R. W. Wood.) Uber die Uberffihrung des Resonanzspektrums der Jod- fluoreszenz in ein Bandenspektrum durch Zumischung von Helium. Verh. Phys. Ges. Berlin, 13, 84-87.

1911. (With R. W. Wood.) Uber die Uberffihrung des Resonanzspektrums der Jod- fluoreszenz in ein Bandenspektrum durch Zumischung von Helium. Phys. Z- 12, 81-83.

1911. (With R. W. Wood.) Transformation of a resonance spectrum into a band-spectrum by presence of helium. Phil. Mag. 21, 265-268.

1911. (With P. Pringsheim.) Uber das elektrische und optische Verhalten der Chlorflamme. Verh. Phys. Ges. Berlin, 13, 328-334.

1911. (With L. Meitner.) Uber radioaktive Ionen. Verh. Phys. Ges. Berlin, 13, 671-675.1911. (With G. Hertz.) Uber einen Zusammenhang zwischen Quantenhypothese und

Ionisierungsspannung. Verh. Phys. Ges. Berlin, 13, 967-971.1911. (With R. Pohl.) Bemerkung zu den Versuchen des Hrn. Marx uber die

Geschwindigkeit der Rontgenstrahlen. Ann. Phys. Lpz. 34, 936-940.1911. (With W. Westphal.) On the question of valency in gaseous ionization. Phil. Mag.

22, 547-551.1912. (With W. Westphal.) Uber eine Beeinflussung der Stossionisation durch Fluoreszenz.

Verh. Phys. Ges. Berlin, 14, 159-166.1912. (With G. Hertz.) Bemerkung zu unserer Notiz liber einen Zusammenhang

zwischen Ionisierungsspannung und Quantenhypothese. Verh. Phys. Ges. Berliny14, 167-168.

1912. Uber die Uberfuhrung des Resonanzspektrums der Jodlluoreszenz in ein Bandenspektrum durch zugemischte Gase. Verh. Phys. Ges. Berlin, 14, 419-422.

1912. (With G. Hertz.) Uber durch polarisiertes Licht erregte Fluoreszenz von JoddampL Verh. Phys. Ges. Berlin, 14, 423-425.

1912. (With G. Hertz.) Uber eine Methode zur direkten Messung der mittleren freien Weglange von Gasmolekiilen. I. Verh. Phys. Ges. Berlin, 14, 596-604.

1912. (With R. Pohl and P. Pringsheim.) Erwiderung an Herrn Marx. Verh. Phys. Ges. Berlin, 14, 1124-1125.

1912. Bericht fiber Ionenbeweglichkeit. Jahrb. Radioakt. u. Elektro?iik. 9, 235-270, 475.1913. (With G. Hertz.) Messung der Ionisierungsspannung in verschiedenen Gasen.

Verh. Phys. Ges. Berlin, 15, 34-44.1913. (With G. Hertz.) Uber Zusammenstosse zwischen Gasmolekiilen und langsamen

Elektronen. Verh. Phys. Ges. Berlin, 15, 373-390.1913. (With G. Hertz.) Notiz fiber Bildung von Doppelschichten. Verh. Phys. Ges. Berliny

15, 391-393.1913. Uber den Einfluss der Elektronenaffinitat auf die Ladung von Kanalstrahlen.

Phys. Z • 14, 623-624.

James Franck 69



*I£"62 *£ ‘UUX9E[ 'Sd0 'HxdA ’uop^siuoissojg joqn uoSunqjouiog ‘2261>61 >61 ‘£ ‘s<cVd

-111(09; ‘jdurepjoqqsqoori^) uoa uopu^qsuopdaosqy oip aoqfj (*NvmxoH0 *a\ qqM.) 2261'991-191 ‘II 's<cVd •ainojBMqnsspari^

aiSaaaSuu qajnp uainqajouijjcasjassBM uoa SunSapaz JaqQ ('oihvq ■£) HUM.) ‘2261'091-991

‘H ‘StCi/j ~y •suimpjq sap §unuundss§unjaisiuoj pun -sSunSajuy jaqn Sunqjauiag 'ZZ6\‘992-692 ‘6 '^d '•I3djo'S

jopuoqrqS uoissiuiououoJiqoig oip pun ossozojg oqosiuioqoojoqd ‘zuozsoaonjg joqn uoSunjoSjog opuoqoiz nz pu^psso'g pun upj^j uoa ouooqjL jop sn^ oSxuxg ’2261

•Ufr-99 f‘Qff-lff ‘Wr60t ‘169-889 ‘22 -uauoj^g jauiusSutqossoig qoanp uojnqojojAj pun uouio^y uoa uopt’siuoj pun SunSoju^jqoiq aoqQ *1261

’69-99 ‘9 '2 •3IWI°JA[ -raiSaraSireuoppzossiQ oip jn^ sopppouSizjy soup ssnyuig uop JoqQ (•nvihxohq *a\ q}qv\) *1261

*2£t”82fr s«yj *2' qi?quijpuouo.i}3pjg[ jop Sunssojy oqospdo oup joqfj *1261 *66'68 ‘f %sHd *2' *3UJO}V 3}83J98ve joqn uoSunqjouiog ('NYmio^g *a\ qiJM) 1261

* 18'ZZ. 'dd S9QuimiM xdS}vyi *Mps%Md *uoiuijpxi}qodg uoa §unjo;pjqjo^\ oip joqn uoSunqjouiog * X 261

‘292-2^2‘98 '9;?jlv 'n -fm;vj\[ -\(os;ndQ -sdQ 'qMyi *ouooq;uio}y uoqosfijqog aop pm Su^q -uouiumsnz mi sossoisuouojjqojg sop opoqjoj/\[ oip pun uoqo^s^j^ oqosidoqsoj^qodg *0261

*£0£ *92’SojdTirepjoqjisqoon^) sop uoiuqjmiqodg uoa uoSunuu'edssSungoauy aoqfj *0261

‘62-81 ‘2 'stCHd '2•sojdumpjoqqsqoori^) sop opq}uoiodsSun§ojuy oip joqfj (-NdOdSNig *g PPM) *0261

*2££’02£‘l '*<fyd *2' ’sumipjj sop uoSunuuudssSunSojuy oip joqQ (-ONidaiNTg ‘g PPM) *0261

*091-^91 ‘l ’Hd'2 ‘uinqaqjeg pun uxmpH iaqQ (-aHoia-g g quM) ‘0261 *01 "2 *1 's^Hd *2" ’uojôdsuouog ui SunjpjjoAs^qsuojuj oip joqn uoSunqjouiog ‘0261

‘ZZL-QZL ‘126ut]X9ff -S9Q 9s<fi(d %HxdA *3I0^3I°IA[ qoqj'esuoppzossiQ jop pun uopusiuoi-ssojg uoqosiMz Su^quomm^sn^ uoup joqfj (maorya^j *x pun ONiddiNrjj g qpM) *6161 ‘SSt'ISt 0Z *2* 'slld ’smnippj sop uoSunuu'edssgumoisiuoj oiq (‘ONiddiN^j *g qpA\) ’6161

"9-H-2SI ‘02 ’2 's<Cl/d •uainqapmsnQ pui uauoaiqaig jom'BsSu^j osso^suomm^sn^ uoqosps'epun jop uoSunqonsaoûjQ ipjnp mnj^qodg uoqospdo nil ouooq;mo;y uoqos(aqog jop §un§p^;sog oiq (’zxdapi *Q PPM) *6161

‘9\f-60t‘L\ *2" *s^Hd ‘s'bq ui uouoj pun uouoj^qojg uoa qpoui^j JoqQ (*zxuaH ‘Q HPA\) ‘9161

*022"£I2 48I ‘uijjidfj -S9Q 's<Ci/j 'yÂ *uoqosimo§s^Q ui Sunpiq iuoiuuii]0 jop pq m;qodss^Q aop ;^psuoûj oAp^pj oip JoqQ (*zxuaH *Q PPM) *9161

*Z,I9“219 *91 ‘UUX33 %SdO 's^ld *HXdA *9ssq^suouoj;qo|g qojnp rlrl 9*££2 ^PHzuûosojaoqpsqoon^) jop SuuSojjq oip aoqQ (*zxHapj o qpA\) *^161

’L9f-LSb ‘91-S9Q 'sti(d %yx*A ’uoqpssop Sunuu^dssSumoisiuoj oip pun sojdm^pjoqpsqoonQ sop uojmpjojy uop pun uouoa^qojg uoqosiMz osso^suomm^sn^ ^qf! (’zxdaQ *Q q}JA\) ’161

*89^£*91 ‘u}lX9S[ *SdQ 's6h{d *HXdA ’uouoj OAiqsod qojnp uop^siuoj Joqfj (mHvg ‘A *g qqA\) *^161 ’61-21 ‘91 ‘mpsg-S3Q -f<Cyj -yÂ -uopusiuoissojs jap auoaq p jnZ (-zxaaH ’O quM) >161

>111-9111 ‘H '2 qquuqjuuauojjqaigpun uop'Bsiuoisso^g uoqosiMz Su^quomm'esn^ uoup JoqQ (’zxuajj *Q qqAV) *8161

>96-626 ‘91 ‘uni3d 'S3D ‘Hd 'HX3A UBUuqjnuauojjqaiq pun uopastuoissojq uaqasiMZ 3uuquauiuiusnZ uaup JaqQ (‘zxaaj^ 'O qiJM) "9161

’029-919 ‘91 ‘ui]X3g -S3Q -stCyg -yx3A 'll -uainqapuisao pun uouo.uq;)]q u;)un?sSm:[ uaqosiMz assqjsuauiuiusn^ .K)C];q (-zxaajq Q qii,\\) "9161

sxiouidjAi poii{(}vi2oig O

on May 24, 2018 http://rsbm.royalsocietypublishing.org/ Downloaded from


James Franck y i1923. (With G. Cario.) Uber sensibilisierte Fluoreszenz von Gasen. Phys. 17, 202-212.1923. Uber sensibilisierte Fluoreszenz von Gasen. Phys. 24, 450-451.1923. (With P. Pringsheim.) Fluoreszenz von Gasen. Naturwissenschaften, 11, 559-563.1923. Neuere Erfahrungen uber quantenhaften Energieaustausch bei Zusammenstossen

von Atomen und Molekiilen. Erg. Exact. Naturw. 2, 106-123.1924. Zur Frage nach der Ionisierungsspannung positiver Ionen. phys. 25, 312-316.1924. Atome und Molekfilstosse und ihre chemische Bedeutung. Naturwissenschaften, 12,

1063-1068.1925. Excitation of light by impacts (in Czech). Cas. pro. pest, matemat. a fys. 54, 377-389.1925. (With M. Born.) Bemerkungen uber die Dissipation der Reaktionswarme. Ann.

Phys. Lpz. 76, 225-230.1925. (With M. Born.) Quantentheorie und Molekelbildung. Z- Phys. 31, 411-429.1925. (With P. M. S. Blackett.) Anregung von Spektren des Wasserstoffs durch Elek-

tronenstoss. Z- Phys. 34, 389-401.1925. Elementary processes of photochemical reactions. Trans. Faraday Soc. 21, 536-542.1925. Quantenchemische Probleme chemischer Reaktionen. Z- Elektrochem. 31, 350-357.1926. (With G. Cario.) Uber die Ausloschung der Resonanzfluoreszenz des Quecksilbers

durch Gaszusatz. Z- Phys. 37, 619-624.1926. Der Wirkungsquerschnitt bei atomaren Stossprozessen. Naturwissenschaften. 14,

211-214.1926. Elementarprozesse photochemischer Reaktionen. (Bemerkungen uber die homoopolare

Bindung.) Z- Phys. Chem. 120, 144-156.1926. (With P. J ordan.) Anregung von Quantensprfingen durch Stosse. Handb. d. Phys.

(first ed.) 23, 641-775.1927. (With H. K uhn and G. Rollefson.) Beziehung zwischen Absorptionsspektren und

chemischer Bindung bei Alkalihalogeniddampfen. Z- Phys. 43, 155-163.1927. (With H. K uhn.) Uber ein Absorptions- und ein Fluoreszenzspektrum von Silber-

jodidmolekfilen und die Art ihrer chemischen Bindung. Z- Phys. 43, 164-171.1927. (With T. R. Hogness.) Uber den Nachweis der Relativgeschwindigkeit der

Zerfallsprodukte bei optischen Dissoziationsprozessen. Z> Phys. 44, 26-31.1927. (With H. K uhn.) Ubrr Absorption und Fluoreszenz von Silberbromid- und Silber-

chloriddampf. Z- Phys. 44, 607-614.1927. Uber eine Rotverschiebung der Resonanzfluoreszenz durch vielfach wiederholte

Streuung. Naturwissenschaften, 15, 236-238.1927. Nobelvortrag, 11. December 1926. Stockholm, Imprimerie Royale.1928. Bandenspektrum und chemische Bindung. Atti del Congr. Intern. Fis. (Como, 1927), 1,

65-71 (Bologna).1928. Einige wichtige experimentelle Grundlagen der Bohr’schen Atomtheorie. Z- Phys.

Chem. Unterr. 41, 18-27.1928. Beitrag zum Problem der Wiedervereinigung von Ionen und Elektronen. Z* Phys. 47,

509-516.1928. A few remarks on the problem of the recombination of positive ions and electrons.

J. Franklin Inst. 205, 473-479.1928. (With G. E. Gibson.) Notiz fiber die Ausloschung der D-Linien in Flammen durch

Chlorzusatz. Z- Phys. 50, 691.1928. (With G. Scheibe.) Uber Absorptionsspektren negativer Halogenionen in Losung. z Phys. Chem. A139, 22-31.1928. Energie-Stufen von Atomen und Molekfilen und ihre Beziehung zur chemischen

Bindung. Ber. Dtsch. Chem. Ges. 61B, 445-459.1928. (With H. Sponer.) Beitrag zur Bestimmung der Dissoziationsarbeit von Molekfilen

aus Bandenspektren. Nachr. Ges. Wiss. Gottingen, Math.-Phys. Klasse, pp. 241-253.1929. (With A. von H ippel.) Der elektrische Durchschlag und Townsend’s Theorie.z Phys. 57, 696-704.



y2 Biographical Memoirs1930. Bestimmung thermochemischer Grossen aus spektroskopischen Daten.

36, 581-589.1930. (With E. R a binow itch .) Uber die Aktivierungswarme bimolekularer Gasreaktionen

und iiber die Chlorknallgasreaktion. Z Elektrochem. 36, 794-799.1930. (With M. Bo r n .) Beitrag zum Problem der Adsorptionskatalyse. Ges.

Gottingen, Math.-Phys. Klasse, pp. 77-89.1931. Beziehungen zwischen Spektroskopie und Chemie. 19, 217-225.1931. (With F. H a b e r .) Zur Theorie der Katalyse durch Schwermetallionen in wassriger

Losung und insbesondere zur Autoxydation der Sulfitlosungen. Sb. Preuss. Akad. Wiss. Phys. Math. Klasse, pp. 250-256.

1932. (With H. Spo ner and E. T e ller .) Bemerkungen uber Pradissoziationsspektrendreiatomiger Molekiile. Z- Phys. Chem. B18, 88-101.

1932. (With H. K u h n .) Schlusse auf Bindungsfestigkeit und Bindungsart aus kontinuier-lichen Absorptionsspektren. Naturwissenschaften, 20, 293-295.

1933. (W ith H. K uhn.) Conclusions on the strength and nature of binding from thecontinuous absorption spectrum. Bull. Acad. Sci. Utd Provinces Agra and Oudh, Allahabad, 2, 223-226.

1933. (With A. Eucken.) Umsatz von Translationsenergie in Schwingungsenergie bei molekularen Stossprozessen. Z- Phys. Chem. B20, 460-466.

1933. Uber den Losungszustand des Wasserstoffs im Palladium und Hydrierungskatalyse.Nachr. Ges. Wiss. Gottingen, Math. Phys. Klasse, pp. 293-296.

1934. (With R. W. W ood .) Ultraviolet absorption of heavy water vapor. Phys. Rev. 45,667-668.

1934. (With E. R abinow itch .) Some remarks about free radicals and the photochemistryof solutions. Trans. Faraday Soc. 30, 120-130.

1935. Beitrag zum Problem der Kohlensaure-Assimilation. Naturwissenschaften, 23, 226-229.1935. (With H . L e v i.) Zum Mechanismus der Sauerstoff-Aktivierung durch fluoreszenz-

fahige Farbstoffe. Naturwissenschaften, 23, 229-230.1935. (With H. L e v i.) Beitrag zur Untersuchung der Fluoreszenz in Flussigkeiten. Phys.

Chem. B27, 409-420.1935. Remarks on photosynthesis. Chem. Rev. 17, 433-438.1936. (With R. W. W ood .) Fluorescence of chlorophyll in its relation to photochemical

processes in plants and organic solutions. J. Chem. Phys. 4, 551-560.1937. (With K . F. H er zfeld .) Remarks on the photochemistry of polyatomic molecules.

' J.Phys. Chem. 41, 97-107.1937. (With K. F. H er zfeld .) An attempted theory of photosynthesis. J. Chem. Phys. 5,

237-251.1937. Fundam entals of photosynthesis. J. Wash. Acad. Sci. 27, 317-329.1938. (With E. T e ller .) Migration and photochemical action of excitation energy in

crystals. J. Chem. Phys. 6, 861-872.1939. (With C. A. R ieke.) Note on the explanation of the D-lines in the spectrum of the

night sky. Astrophys. J . 89, 463-464.1940. (With R . L ivingston .) Assimilation and respiration of excised leaves at high con

centrations of carbon dioxide. Amer. J. Bot. 27, 449-458.1941. (With H. G a ffr o n .) Photosynthesis; facts and interpretations. Adv. Enzymology, 1,

199-262.1941. (W ith R. L ivingston .) Remarks on the fluorescence, phosphorescence and photo

chemistry of dyestuffs. J. Chem. Phys. 9, 184-190.1941. (With K. F. H er zfeld .) Contribution to a theory of photosynthesis. J. Phys. Chem.

45, 978-1025.1941. (With C. S. F rench and T. T. P uck .) The fluorescence of chlorophyll and photo

synthesis. J. Phys. Chem. 45, 1268-1300.1941. (With S. W e ller .) Photosynthesis in flashing light. J . Phys. Chem. 45, 1359-1373. 1941. (With C. S. F r enc h .) Photoxidation processes in plants. J. Gen. Physiol. 25, 309-324.



731941. Some fundamental aspects of photosynthesis. Sigma Xi Quart. 29, 81-105.1942. Carbon dioxide evolution during the induction period of photosynthesis. Amer. J. Bot

29, 314-317.1943. (With P. P ringsheim .) Phosphorescence of adsorbed trypaflavine and its quenching

by oxygen. J . Chem. Phys. 11, 21-27.1945. Photosynthetic activity of isolated chloroplasts. Rev. Mod. Phys. 17, 112-119.1945. (With P. P ringsheim and D. T. L a d .) Oxygen production by anaerobic photo

synthesis of algae measured by a new micromethod. Arch. Biochem. 7, 103-142.1946. Proposal of a method for the separation of He3 from He4. Phys. Rev. 70, 561.1947. (With Y. G. S h ia u .) Chlorophyll fluorescence and photosynthesis in algae, leaves

and chloroplasts. Arch. Biochem. 14, 253-295.1947. (With J. E. M a y e r .) An osmotic diffusion pump. Arch. Biochem. 14, 297-313.1948. Bemerkungen liber Lumincszenz von Ionenkristallen. Ann. Phys. Lpz. 3, 62-68.1948. (With H. S p o n e r .) Comparison between predissociation and internal conversion in

polyatomic molecules. In Contribution a VEtude de la Structure Moleculaire (Vol. Commemoratif Victor Henri), pp. 169-179. Liege: Desoer.

1948. (With A. H. B r o w n .) On the participation of carbon dioxide in the photosyntheticactivity of illuminated chloroplast suspensions. Arch. Biochem. 16, 55-60.

1949. (With R. L ivingston .) Remarks on intra- and inter-molecular migration of excitationenergy. Rev. Mod. Phys. 21, 505-509.

1949. Possibility of photosynthesis on Mars. In The atmospheres of the Earth and planets (G. P.Kuiper, ed.), pp. 355-356. Univ. of Chicago Press.

1949. An interpretation of the contradictory results in measurements of the photosynthetic quantum yields and related phenomena. Arch. Biochem. 23, 297-314.

1949. The relation of the fluorescence of chlorophyll to photosynthesis. In Photosynthesis in Plants (J. Franck & W. E. Loomis eds.), 293-348. Ames, Iowa: State College Press.

1951. A critical survey of the physical background of photosynthesis. Ann. Rev. Plant Physiol. 2, 53-86.

1951. The physical background of photosynthesis. Symposia Soc. Exper. Biol., No. 5 (Carbondioxide fixation and photosynthesis), pp. 160-175.

1952. (With R. P la tzm an .) Theory of the absorption spectra of halide ions in solution. InL. Farkas Mem. Vol., Res. Council Israel, Spec. Publ. No. 1, 21-36, Jerusalem.

1953. Participation of respiratory intermediates in the process of photosynthesis as anexplanation of abnormally high quantum yields. Arch. Biochem. & Biophys. 45, 190-229.

1954. (With R. P la tzm a n .) The role o f the hydration configuration in electronic processesinvolving ions in aqueous solution. Phys. 138, 411-431.

1954. (With R. P latzm a n .) Physical principles underlying photochemical, radiation-chemical and radiobiological reactions. In Radiation Biology (A. Hollaender ed.), 1, Part 1, 191-253. New York: McGraw-Hill.

1955. Physical problems of photosynthesis. Daedalus Stockh. 86, 17-42.1955. (With F. L. A l len .) Photosynthetic evolution of oxygen by flashes of light. Arch.

Biochem. & Biophys. 58, 124-143.1956. (With H. S po n e r .) Remarks on radiationless transitions in complex molecules.

J. Chem. Phys. 25, 172.1957. General remarks on chorophyll-sensitized photochemical reactions in vitro. In

Research in photosynthesis (H. Gaffron et al., eds.), pp. 19-21. New York: Interscience.1957. A theory of the photochemical part of photosynthesis. In Research in photosynthesis

(H. Gaffron et al., eds.), pp. 142-144. New York: Interscience.1958. (With R. P latzm an .) A physical mechanism for the inactivation of proteins by

ionising radiation. In Symposium on information theory in biology (H. P. Yockey, R. L. Platzman & FI. Quastler, eds.), pp. 262-275. New York: Pergamon.

1958. (With J. E. Br u g g er .) Experimental and theoretical contribution to studies of the afterglow of chlorophyll in plant materials. Arch. Biochem. & Biophys. 75, 465-496.

James Franck



74 Biographical Memoirs1958. Remarks on the long-wavelength limits of photosynthesis and chlorophyll fluorescence.

Proc. Nat. Acad. Sci. Wash. 44, 941-948.1958. Photosynthesis. Technion Yearbook, 15, 39-41.1959. A reply to the comments by Tollin on Franck’s theory of the primary steps in photo

synthesis. Arch. Biochem. & Biophys. 80, 378-382.1960. Fluoreszenz des Chlorophylls in Zellen und Chloroplasten und ihre Beziehungen zu

den Primarakten der Photosynthese. In iDie 2‘ (W. Ruheland ed.),Handb. d. Pflanzenphysiol. 5 (Teil 2), 689-735.

1962. (With J . L. R osenberg & C. Weiss, J r .) The primary photochemical step in photosynthesis: a comparison of two theories. In Luminescence of organic and inorganic materials (H. P. Kallmann & G. M. Spruch, pp. 11-29. New York. VViley.

1963. (With J. L. R osenberg .) Principles of a theory of energy utilisation in photosynthesis. In ‘Photosynthetic mechanisms in green plants’, pp. 101-111, Nat. Acad. Sci. Nat. Res. Council Publ. No. 1145, Washington.

1964. (With J. L. R osenberg .) A theory of light utilisation in plant photosynthesis.Theor. Biol. 7, 276-301.

Book1926. (W ith P. J ordan.) Anregung von Quantenspriingen durch Stosse. Berlin: Springer.

Miscellaneous articles1922. ‘Heinrich Rubens’, Verh. Phys. Ges. Berlin, 3, 76-91.1922. (With R. P ohl.) Rubens und die Quantentheorie. Naturwissenschaften, 10, 1030-1033. 1947. ‘Max Planck’, Yb. Amer. Phil. Soc. pp. 284-291.1963. Niels Bohr’s Personlichkeit, Naturwissenschaften, 50, 341-343.



Documents

James Franck, 1882-1964 - Royal Societyrsbm.royalsocietypublishing.org/content/roybiogmem/11/53.full.pdf · JAMES FRANCK 1882-1964 ... It was at Heidelberg in 1901 or 1902 that he