James Franck

James Franck (Template:IPA; 26 August 1882 – 21 May 1964) was a German–American atomic physicist who shared the 1925 Nobel Prize in Physics with Gustav Hertz "for their discovery of the laws governing the impact of an electron upon an atom".<ref name="Nobel Prize">Template:Cite web</ref>

Franck completed his doctorate in 1906 and his habilitation in 1911 at the Frederick William University in Berlin, where he lectured and taught until 1918, having reached the position of professor extraordinarius. He served as a volunteer in the German Army during World War I. He was seriously injured in 1917 in a gas attack and was awarded the Iron Cross 1st Class.

Franck became the head of the physics division of the Kaiser Wilhelm Gesellschaft for Physical Chemistry. In 1920, Franck became professor ordinarius of experimental physics and Director of the Second Institute for Experimental Physics at the University of Göttingen. While there he worked on quantum physics with Max Born, who was Director of the Institute of Theoretical Physics. His work included the Franck–Hertz experiment, an important confirmation of the Bohr model of the atom. He promoted the careers of women in physics, notably Lise Meitner, Hertha Sponer, and Hilde Levi.

After the Nazi Party came to power in Germany in 1933, Franck resigned from his position at the University of Göttingen in protest against the dismissal of fellow colleagues. He assisted Frederick Lindemann in helping dismissed Jewish scientists find work overseas, before he left Germany in November. After a year at the Niels Bohr Institute in Denmark, he moved to the United States, where he worked at Johns Hopkins University in Baltimore and then the University of Chicago. During this period he became interested in photosynthesis.

Franck participated in the Manhattan Project during World War II as director of the chemistry division of the Metallurgical Laboratory. He was also the Chairman of the Committee on Political and Social Problems regarding the atomic bomb, which is best known for the compilation of the Franck Report, which recommended that the atomic bombs not be used on the Japanese cities without warning.

Education

James Franck was born on 26 August 1882 in Hamburg, Germany, into a Jewish family, the second child and first son of Jacob Franck, a banker, and Rebecca Nachum Drucker.Template:Sfn He had an older sister, Paula, and a younger brother, Robert.Template:Sfn His father was a devout and religious man, while his mother came from a family of rabbis.Template:Sfn

In 1891, Franck enrolled at the Wilhelm-Gymnasium in Hamburg, which was then a boys-only school.Template:Sfn Hamburg had no university then, so prospective students had to attend one of the 22 universities elsewhere in Germany. Intending to study law and economics, In 1901, Franck entered the University of Heidelberg, as it had a renowned law school.Template:Sfn He attended lectures on law, but was far more interested in those on science. While there, he met Max Born, who would become a lifelong friend. With Born's help, he was able to persuade his parents to allow him to switch to studying physics and chemistry.Template:Sfn He attended mathematics lectures by Leo Königsberger and Georg Cantor, but Heidelberg was not strong on the physical sciences, so he decided to go to the University of Berlin.Template:Sfn

At Berlin, Franck attended lectures by Max Planck and Emil Warburg.Template:Sfn For his Ph.D.,Template:Sfn Warburg suggested that he study corona discharges. He found this topic too complex, so he changed the focus of his thesis.Template:Sfn Titled Über die Beweglichkeit der Ladungsträger der Spitzenentladung (On the mobility of ions),Template:Sfn it would subsequently be published in Annalen der Physik.<ref>Template:Cite journal</ref>

With his thesis completed, Franck had to perform his deferred military service. He was called up on 1 October 1906 and joined the 1st Telegraph Battalion. He suffered a minor horse riding accident in December and was discharged as unfit for duty. He took up an assistantship at the Physikalische Verein in Frankfurt in 1907, but did not enjoy it, and soon returned to the University of Berlin.Template:Sfn At a concert, he met Ingrid Josefson, a Swedish pianist. They were married in a Swedish ceremony in Gothenburg on 23 December 1907. They had two daughters: Dagmar "Daggie", who was born in 1909; and Elisabeth "Lisa", who was born in 1912.Template:Sfn

To pursue an academic career in Germany, having a doctorate was not enough; one needed a venia legendi, or habilitation. This could be achieved with either another major thesis or by producing a substantial body of published work. Franck chose the latter route. There were many unsolved problems in physics at the time, and by 1914 he had published 34 articles. He was the sole author of some, but generally preferred working in collaboration with Eva von Bahr, Lise Meitner, Robert Pohl, Peter Pringsheim, Robert W. Wood, Arthur Wehnelt, and Wilhelm Westphal. His most fruitful collaboration was with Gustav Hertz, with whom he wrote 19 articles. He received his habilitation on 20 May 1911.Template:Sfn

Franck–Hertz experiment

Anode current (arbitrary units) versus grid voltage (relative to the cathode). This graph is based on the original 1914 paper by Franck and Hertz.

In 1914, Franck teamed up with Hertz to perform an experiment to investigate fluorescence. They designed a vacuum tube for studying energetic electrons that flew through a thin vapour of mercury atoms. They discovered that when an electron collided with a mercury atom it could lose only a specific quantity (4.9 electronvolts) of its kinetic energy before flying away. A faster electron does not decelerate completely after a collision, but loses precisely the same amount of its kinetic energy. Slower electrons just bounce off mercury atoms without losing any significant speed or kinetic energy.Template:Sfn<ref name=FH1>Template:Cite journal</ref>

These experimental results provided confirmation of Albert Einstein's photoelectric effect and Planck's relation (Template:Nowrap) linking energy (E) and frequency (f) arising from quantisation of energy with the Planck constant (h). But they also provided evidence supporting the model of the atom that had been proposed the previous year by Niels Bohr. Its key feature was that an electron inside an atom occupies one of the atom's "quantum energy levels". Before a collision, an electron inside the mercury atom occupies its lowest available energy level. After the collision, the electron inside occupies a higher energy level with 4.9 eV more energy. This means that the electron is more loosely bound to the mercury atom. There were no intermediate levels or possibilities.Template:Sfn<ref>Template:Cite journal</ref>

In a second paper presented in May 1914, Franck and Hertz reported on the light emission by the mercury atoms that had absorbed energy from collisions. They showed that the wavelength of this ultraviolet light corresponded exactly to the 4.9 eV of energy that the flying electron had lost. The relationship of energy and wavelength had also been predicted by Bohr.Template:Sfn<ref name=FH2>Template:Cite journal</ref> Franck and Hertz completed their last paper together in December 1918. In it, they reconciled the discrepancies between their results and Bohr's theory, which they now acknowledged.Template:Sfn<ref>Template:Cite journal</ref> In his Nobel lecture, Franck admitted that it was "completely incomprehensible that we had failed to recognise the fundamental significance of Bohr's theory, so much so, that we never even mentioned it once".<ref>Template:Cite web</ref> On 10 December 1926, Franck and Hertz were awarded the 1925 Nobel Prize in Physics "for their discovery of the laws governing the impact of an electron upon an atom".<ref name="Nobel Prize" />

World War I

Franck enlisted in the German Army soon after the outbreak of the First World War in August 1914. In December, he was sent to the Picardy sector of the Western Front. He became a deputy officer (offizierstellvertreter), and then a lieutenant (leutnant) in 1915.Template:Sfn In early 1915, he was transferred to Fritz Haber's new unit that would introduce clouds of chlorine gas as a weapon.<ref>Template:Cite journal</ref> With Otto Hahn, he was responsible for locating sites for the attacks. He was awarded the Iron Cross, Second Class, on 30 March 1915,<ref name="Papers">Template:Cite web</ref> and the city of Hamburg awarded him the Hanseatic Cross on 11 January 1916.<ref name="Papers" /> While in hospital with pleurisy, he co-wrote yet another scientific paper with Hertz, and he was appointed an assistant professor in his absence by Frederick William University on 19 September 1916. Sent to the Russian front, he came down with dysentery. He returned to Berlin, where he joined Hertz, Westphal, Hans Geiger, Hahn, and others at Haber's Kaiser Wilhelm Institute for Physical Chemistry and Electrochemistry, working on the development of gas masks.Template:Sfn He was awarded the Iron Cross, First Class, on 23 February 1918. He was discharged from the army on 25 November 1918, soon after the war ended.<ref name="Papers" />

With the war over, Haber's Kaiser Wilhelm Institute now returned to research, and Haber offered Franck a job. His new post came with more pay, but was not a tenured position. It did however allow him to pursue his research as he wished. Working with new, younger collaborators such as Walter Grotrian, Paul Knipping, Thea Krüger, Fritz Reiche, and Hertha Sponer, his first papers at the Kaiser Wilhelm Institute examined atomic electrons in their excited state, results that would later prove important in the development of the laser.Template:Sfn They coined the term metastable for atoms spending an extended time in a state other than that of least energy.Template:Sfn When Niels Bohr visited Berlin in 1920, Meitner and Franck arranged for him to come to the Kaiser Wilhelm Institute to talk with the younger staff without the presence of the bonzen (bigwigs).Template:Sfn

Career in Göttingen

Left to right: Template:Interlanguage link, Max Born, James Franck, and Robert Pohl (the bonzen) in 1923

In 1920, the University of Göttingen offered Max Born its Chair of Theoretical Physics, which had recently been vacated by Peter Debye. Göttingen was an important centre for mathematics, thanks to David Hilbert, Felix Klein, Hermann Minkowski, and Carl Runge, but not so much for physics. This would change. As part of his price for coming to Göttingen, Born wanted Franck to head experimental physics there. On 15 November 1920, he became Professor of Experimental Physics and Director of the Second Institute for Experimental Physics, a fully tenured professor ordinarius. He was allowed two assistants, so he brought Hertha Sponer with him from Berlin to fill one of the positions, and Pohl, a gifted teacher, headed the First Institute and handled the lectures.Template:Sfn<ref name="Nobel bio">Template:Cite web</ref> He refurbished the laboratory with the latest equipment using funds from his own pocket.Template:Sfn

Under Born and Franck, Göttingen was one of the world's great centres for physics from 1920 to 1933.<ref name="Nobel bio"/>Template:Sfn Although they published only three papers together, Born and Franck discussed every one of their papers with each other. Gaining admittance to Franck's laboratory became highly competitive. His doctoral students included Hans Kopfermann, Arthur R. von Hippel, Wilhelm Hanle, Fritz Houtermans, Heinrich Kuhn, and Heinz Maier-Leibnitz.Template:Sfn In supervising doctoral candidates, he had to ensure that thesis topics were well-defined, and would teach the candidate how to conduct original research, while still staying within the limits of the candidate's ability, the laboratory's equipment and the institute's budget.Template:Sfn Under his direction, research was carried out into the structure of atoms and molecules.Template:Sfn

In his own research, Franck developed what became known as the Franck–Condon principle, a rule in spectroscopy and quantum chemistry that explains the intensity of vibronic transitions, simultaneous changes in electronic and vibrational energy levels of a molecule due to the absorption or emission of a photon of the appropriate energy. The principle states that during an electronic transition, a change from one vibrational energy level to another will be more likely to happen if the two vibrational wave functions overlap more significantly.Template:Sfn<ref>Template:Cite journal</ref> The principle has since been applied to a wide variety of related phenomena.Template:Sfn

For his work during this time period, Franck was elected to the American Academy of Arts and Sciences in 1929.<ref>Template:Cite web</ref>

Middle life

This period came to an end when the Nazi Party won power in Germany in an election on 2 March 1933. The following month, it enacted the Law for the Restoration of the Professional Civil Service, which provided for the retirement or dismissal of all Jewish civil servants, along with political opponents of the government. As a veteran of the First World War, Franck was exempt, but he submitted his resignation anyway on 17 April 1933.Template:Sfn He once commented that science was his god and nature was his religion. He did not require his daughters to attend religious instruction classes at school,<ref name="David Nachmansohn 1979 62">Template:Harvnb</ref> and even let them have a decorated tree at Christmas;Template:Sfn but he was proud of his Jewish heritage all the same.<ref name="David Nachmansohn 1979 62"/> He was the first academic to resign in protest over the law.Template:Sfn Newspapers around the world reported it, but no government or university protested.Template:Sfn

Franck assisted Frederick Lindemann in helping dismissed Jewish scientists find work overseas, before he left Germany in November 1933.Template:Sfn After a brief visit to the United States, where he measured the absorption of light in heavy water with Wood at Johns Hopkins University, he took up a position at the Niels Bohr Institute in Copenhagen.Template:Sfn He needed a new collaborator, so he took on Hilde Levi, whose recent thesis had impressed him.Template:Sfn His original intention was to continue his research into the fluorescence of vapours and liquids, but under Bohr's influence they began to take an interest in biological aspects of these reactions, particularly photosynthesis, the process by which plants use light to convert carbon dioxide and water into more organic compounds. Biological processes turned out to be far more complicated than simple reactions in atoms and molecules. He co-authored two papers with Levi on the subject, which he would return to over the following years.Template:Sfn<ref> Template:Cite journal</ref><ref> Template:Cite journal</ref>

Franck found a position at the Polytekniske Læreanstalt in Copenhagen for Arthur von Hippel, who was now his son in law, having married his daughter Dagmar. He decided to provide financial security for his children by dividing his Nobel Prize money between them. The gold medal itself was entrusted to Niels Bohr for safekeeping.Template:Sfn When Germany invaded Denmark on 9 April 1940, the Hungarian chemist George de Hevesy dissolved the gold medal, along with that of Max von Laue in aqua regia to prevent the Germans from taking them. He placed the resulting solution on a shelf in his laboratory at the Niels Bohr Institute. After the war, he returned to find the solution undisturbed and precipitated the gold out of the acid. The Nobel Society then recast the Nobel Prize medals.Template:Sfn<ref>Template:Cite web</ref>

In 1935, Franck moved to the United States, where he had accepted a professorship at Johns Hopkins University.Template:Sfn The laboratory there was poorly equipped compared to the one in Göttingen, but he received $10,000 for equipment from the Rockefeller Foundation. A more intractable problem was that the university had no money to hire skilled staff. Franck was concerned about his family members remaining in Germany, and needed money to help them emigrate. He therefore accepted an offer from the University of Chicago, where his work on photosynthesis had attracted interest, in 1938.Template:Sfn

Franck's first paper there, co-authored with Edward Teller, was on photochemical processes in crystals.Template:Sfn Hans Gaffron became his collaborator.Template:Sfn They were joined by Pringsheim, who escaped from Belgium after the German invasion. Franck arranged a position for Pringsheim at his laboratory.Template:Sfn Both his daughters and their families moved to the United States, and he was also able to bring out his elderly mother and aunt.Template:Sfn He became a naturalized US citizen on 21 July 1941,<ref name="Papers"/> so he was not an enemy alien when the United States declared war on Germany on 11 December 1941. His daughters still were, though, so they were restricted from travelling, and could not take care of their mother when she fell ill and died on 10 January 1942, although they were permitted to attend her funeral.Template:Sfn

In February 1942, Arthur Compton established its Metallurgical Laboratory at the University of Chicago. As part of the Manhattan Project, its mission was to build nuclear reactors to create plutonium that would be used in atomic bombs.Template:Sfn The Metallurgical Laboratory's Chemistry Division was initially headed by Frank Spedding, but he preferred hands on work to administration. Compton then turned to Franck, with some trepidation owing to his German background.Template:Sfn Compton later wrote:

In addition to heading the Chemistry Division, Franck was also the chairman of the Metallurgical Laboratory's Committee on Political and Social Problems regarding the atomic bomb, which consisted of himself and Donald J. Hughes, J. J. Nickson, Eugene Rabinowitch, Glenn T. Seaborg, J. C. Stearns and Leó Szilárd.<ref name="Nina Byers" /> In 1945, Franck warned Henry A. Wallace of their fears that "mankind has learned to unleash atomic power without being ethically and politically prepared to use it wisely."Template:Sfn The committee compiled what became known as the Franck Report. Finished on 11 June 1945, it recommended that the atomic bombs not be used on the Japanese cities without warning.<ref name="Nina Byers">Template:Cite journal</ref> In any event, the Interim Committee decided otherwise.Template:Sfn

Later life

Left to right: Niels Bohr, James Franck, Albert Einstein, and Isidor Rabi in 1954

Franck married Hertha Sponer in a civil ceremony on 29 June 1946,Template:Sfn after his first wife, Ingrid, died in 1942. In 1947, he became professor emeritus at the University of Chicago, but continued to work there to tackle the problem of explaining the mechanism of photosynthesis. Meitner saw no break between his early and later work. She recalled that:

In addition to the Nobel Prize, Franck was awarded the Max Planck Medal of the German Physical Society in 1951, and the Rumford Prize of the American Academy of Arts and Sciences in 1955 "for his studies in the investigation of photosynthesis". He became an honorary citizen of Göttingen in 1953,Template:Sfn was elected a Member of the National Academy of Sciences in 1944,<ref>Template:Cite web</ref> and elected a Foreign Member of the Royal Society (ForMemRS) in 1964.Template:Sfn He was also an International Member of the American Philosophical Society.<ref>Template:Cite web</ref>

Franck died suddenly of a heart attack while visiting Göttingen on 21 May 1964 at the age of 81.Template:Sfn He is buried in Chicago with his first wife.Template:Sfn

In 1967, the University of Chicago named the James Franck Institute after him.<ref>Template:Cite web</ref> A lunar crater has also been named in his honour.<ref>Template:Cite web</ref> His papers and recast Nobel Prize medal are located in the University of Chicago Library.<ref name="Papers"/>

See also

• List of Jewish Nobel laureates

References

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Further reading

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External links

• Oral history interview transcript with James Franck on 9 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session I
• Oral history interview transcript with James Franck on 10 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session II
• Oral history interview transcript with James Franck on 11 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session III
• Oral history interview transcript with James Franck and Hertha Sponer Franck on 12 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session IV
• Oral history interview transcript with James Franck and Hertha Sponer Franck on 13 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session V
• Oral history interview transcript with James Franck and Hertha Sponer Franck on 14 July 1962, American Institute of Physics, Niels Bohr Library & Archives—Session VI
• Template:Nobelprize including the Nobel Lecture, 11 December 1926: "Transformation of Kinetic Energy of Free Electrons into Excitation Energy of Atoms by Impacts"