Davisson, Clinton Joseph

(b. Bloomington, Illinois, 22 October 1881; d. Charlottesville, Virginia, 1 February 1958)

physics.

Davisson’s father, Joseph, was a contract painter and his mother, Mary Calvert Davisson, a school-teacher. After graduating from Bloomington High School in 1902, Davisson entered the University of Chicago. He interrupted his second year to teach physics briefly at Purdue University. In 1905 he moved to Princeton University as instructor in physics, working primarily as research assistant to O. W. Richardson. Returning to Chicago for summer sessions, Davisson earned his B. S. from the university in 1908 and was awarded his Ph.D. in physics (with a minor in mathematics) at Princeton in 1911. On 4 August 1911 he married Charlotte Sara Richardson, sister of O. W. Richardson, and that summer was appointed assistant professor of physics at Carnegie Institute of Technology. While there he published on Bohr’s atomic theory.

In 1917, on leave from Carnegie Institute, Davisson moved to the engineering department of the Western Electric Company Laboratories (now Bell Telephone Laboratories) to participate in a project on military telecommunications, intending to return to Carnegie Institute. After the war, however, he decided not to go back to his heavy teaching responsibilities but to remain at the laboratories, where he had been guaranteed freedom to do full-time basic research, an uncommon condition in commercial laboratories at that time.

At Western Electric, Davisson was involved mainly in two different areas of research: thermionics and emission of electrons from metals under electron bombardment. In thermionics one of his more important experiments was the measurement of the work functions of metals, the results of which suggested that the conduction electrons in a metal do not always have the normal thermal energy predicted by classic theory. Davisson’s interest in secondary electron emissions started when he and C. H. Kunsman accidentally discovered in 1919 that a few secondary electrons from nickel under electron bombardment have the same energy as the primary electrons. They went on to measure the distribution-in-angle of these secondary electrons and found it to have two maximums. In the years that followed, they repeated these experiments with various metals while Davisson made unsuccessful efforts to understand these results theoretically.

Davisson’s investigations on the scattering of electrons entered a new phase when, in April 1925, his target was heavily oxidized by an accidental explosion of a liquid-air bottle. He cleaned the target by prolonged heating and then found the distribution-in-angle of the secondary electrons completely changed, now showing a strong dependence on crystal direction. He traced this change to a recrystallization caused by the heating. Prior to the accident the target had consisted of many tiny crystals, but the heating converted it to several large crystals. Davisson and L. H. Germer, who had replaced Kunsman before the accident, at once began bombarding targets of single crystals.

In the summer of 1926 Davisson attended a meeting of the British Association for the Advancement of Science at Oxford. There he discussed his investigations of the scattering of the electrons with Max Born, James Franck, and others. For the first time he heard in detail about Louis de Broglie’s hypothesis that an electron possesses a wave nature and has a wavelength h/mv, where h is Planck’s constant, m the electron mass, and v the speed of the electron. The Oxford discussions persuaded Davisson that his experimental results were probably due to the effects of de Broglie waves. This interpretation of the earlier Davisson-Kunsman experiments had already been suggested, a year prior to the meeting, by Walter Elsasser, who carried out experiments himself, trying to confirm his point without success. Davisson knew of Elsasser’s suggestion but, failing to find any evidence of a wave phenomenon, dismissed it as irrelevant. Elsasser therefore had no influence on the course of Davisson’s experiments, and it was not until the Oxford conference that Davisson became fully aware of what his experimental results might reveal.

When Davisson returned from England, he and Germer began a systematic search for some sort of interference phenomenon, and in January 1927 they observed electron beams resulting from diffraction by a single crystal of nickel. The results were in good agreement with de Broglie’s prediction. For his confirmation of electron waves Davisson shared the Nobel Prize in physics in 1937 with G. P. Thomson, who had independently confirmed electron waves by a different method.

In the 1930’s Davisson continued to show an interest in electron waves, especially in their application to crystal physics and electron microscopy, developing a technique for electron focusing. He retired from the Bell Telephone Laboratories in 1946. From there he moved to the University of Virginia as a visiting professor of physics and retired in 1954.

BIBLIOGRAPHY

I. Original Works. Davisson’s writings, include “Dispersion of Hydrogen and Helium on Bohr’s Theory,” in Physical Review, 2nd ser., 8 (1916), 20–27; “Scattering of Electrons by Nickel,” in Science, n. s. 54 (1921), 522–524, written with C. H. Kunsman; “Thermionic Work Function of Tungsten,” in Physical Review, 2nd ser., 20 (1922), 300–330, written with L. H. Germer; “Scattering of Electrons by a Positive Nucleus of Limited Field,” ibid., 21 (1923), 637–649; “Scattering of Low Speed Electrons by Platinum and Magnesium,” ibid., 22 (1923), 242–258, written with C. H. Kunsman; “Diffraction of Electrons,” ibid., 30 (1927), 705–740, written with L. H. Germer; “Scattering of Electrons by a Single Crystal of Nickel,” in Nature, 119 (1927), 558–560, written with L. H. Germer; “Reflection and Refraction of Electrons by a Crystal of Nickel,” in Proceedings of the National Academy of Sciences of the United States of America, 14 (1928), 619–627, written with L. H. Germer; and “Reflection of Electrons by a Crystal of Nickel,” ibid., 317–322, written with L. H. Germer.

Original MSS are listed in T. S. Kuhn et al., Sources for History of Quantum Physics (Philadelphia, 1967), p. 31; and The National Union Catalog of Manuscript Collections 1963–1964 (Washington, D.C., 1965), p. 253.

II. Secondary Literature. On Davisson or his work, see K. K. Darrow, “A Perspective of Davisson’s Scientific Work,” in Biographical Memoirs. National Academy of Sciences, 36 (1962), 64–79; W. Elsasser, “Bemerkungen zur Quantenmechanik freier Elektronen,” Die Naturwissenshaften, 13 (1925), 711; L. H. Germer, “Low-Energy Electron Diffraction,” in Physics Today, 17 , no. 7 (July 1964), 19–23; M. Jammer, The Conceptual Development of Quantum Mechanics (New York, 1966), pp. 189, 250–253; and M. J. Kelly, “Clinton Joseph Davisson,” in Biographical Memoirs. National Academy of Sciences, 36 (1962), 51–62. For more extensive bibliographical listings, see Poggendorff, VIIb, pt. 2 (1967), 994; and Biographical Memoirs. National Academy of Sciences, 36 (1962), 81–84.

Kenkichiro Koizumi