DUMOND, JESSE WILLIAM MONROE

(b. Paris, France, 11 July 1892; d. Pasadena, California, 4 December 1976)

experimental physics.

DuMond’s long and productive scientific career embraced studies in atomic physics by the use of X rays, nuclear spectroscopy, and measurements of the fundamental physical constants.

He was the only child of Fredrick Melville DuMond, an artist and teacher, and of Louise Adéle Kerr DuMond, also an artist, who came from a well-to-do Philadelphia family living in Paris. After his mother died in 1894, he was brought up by his maternal grandmother and grandaunt in Paris, and then by his father’s parents in Rochester, New York, and later in Monrovia, California. DuMond’s later passion for designing and building intricate, precision scientific apparatus was sparked by his grandfather, Alonzo Monroe DuMond, a sailor turned sheetmetal artisan. Under his grandfather’s guidance, DuMond learned how to design and build mechanical objects using cast-off and homemade materials, from toys to phonographs to telephones.

After graduation from Monrovia High School, DuMond worked at a number of jobs for a year and then, in 1912, entered Throop College (now the California Institute of Technology). He received a B.S. in electrical engineering in 1910. For his thesis DuMond designed and constructed a harmonic analyzer—a mechanical calculator that, he felt, better met the needs of the average laboratory than A. A. Michelson and S. W. Stratton’s patented device.

DuMond spent the years 1916 and 1917 as an electrical engineer at the General Electric Company in Schenectady, New York. While there, he took graduate courses at Union College under an arrangement between the company and the school, earning a master’s degree (1919) in electrical engineering. The tedious numerical calculations in an advanced course on alternating-current problems inspired his master’s thesis, a complex quantity slide rule, a device he once characterized as a substitute for routine work, not intelligence. In 1918, disenchanted with industrial work, DuMond joined the U.S. Army to fight with the American Expeditionary Force in France. He served at the front with a sound-ranging company until the armistice. Upon discharge, DuMond spent one year (1919–1920) as a design draftsman at the French Thomson-Houston Company in Paris and another (1920–1921) at the National Bureau of Standards in Washington, D. C.

DuMond married Irene Gaebel in 1920; they had a son and two daughters. He and Irene were divorced in 1942, and that same year he married Louise Marie Baillet.

In 1921 he returned to Caltech as a graduate student, and he obtained a Ph.D. in physics in 1929. Under physicist Robert A. Millikan’s leadership, the school had just embarked on an ambitious research program in physics. In DuMond, Millikan found a relentless, frugal researcher; a producer ofingenious equipment; and an idealist, a man fiercely loyal to the institute, Except for a brief period as visiting associate professor at Stanford University, in 1931, DuMond remained on the Caltech faculty for thirty-four years. He climbed the academic ranks slowly, partly because he voluntarily resigned a graduate teaching fellowship in 1924 to devote more time to research, partly because of the Depression. After spending nine years (1929–1938) as an unpaid research fellow, DuMond became an associate professor. In 1946 he was promoted to full professor, and in 1963 he became professor emeritus.

DuMond’s doctoral dissertation dealt with the Compton scattering of X rays by atoms, and the breadth and structure of the shifted line. In his derivation of the shift in 1922, Arthur Compton had assumed an elastic collision between a photon of light and an electron at rest. But if the atomic electrons had an initial momentum, DuMond reasoned, that momentum could explain the observed broadening of the shifted lines. Using this hypothesis, in 1925 he undertook a detailed spectral study of the Compton line. Now considered one of the classical experiments of atomic physics, DuMond’s measurements provided the first direct experimental evidence of the momentum distribution of electrons in atoms, as had been predicted by wave mechanics.

DuMond sought greater intensity and contrast in an X-ray spectroscopic instrument. Therefore, with Harry A. Kirkpatrick (his first graduate student) he conceived, designed, and built a multicrystal spectrometer in 1929, Consisting of fifty small, individual calcite crystals, it was the first of severalingenious spectrometers DuMond developed to study Compton line broadening, (In 1964 DuMond and Kirkpatrick donated this spectrometer to the Smithsonian Institution, Washington, D.C.) Another unique piece of equipment, the curved crystal focusing spectrometer, followed in 1934. It was particularly useful in the high-energy region, where high resolution is hard to secure. Eager to extend the technique developed for high-energy X-ray studies to nuclear physics, DuMond in 1937 designed a large focusing bent-crystal gamma-ray spectrometer. An immediate success when tested after World War II, this new instrument for measuring gamma-ray frequencies became an important research tool in the hands of nuclear spectroscopists at Caltech and elsewhere. DuMond collaborated on a wide range of gammaray studies in Pasadena, from analyzing the nuclear energy levels in rare earth nuclei to measuring with extraordinary precision the wavelengths of gamma rays emitted by more than a score of nuclides.

DuMond’s work on the fundamental physical constants began in the early 1930’s, in response to several independent reports that Millikan’s 1917 oildrop value of the electron charge c was about 0.6 percent too low. Convinced that the discrepancy in measurements was “one of those small errors in our bookkeeping of nature’s accounts, behind which there may hide something of great interest and importance” (as he wrote in a letter to L. L. Watters, 11 January 1935), DuMond and his students studied topics ranging from the validity of X-ray methods of determining the charge on the electron to determining the ratio of h/e (where h is Planck’s constant) from the short wavelength limit of the continuous X-ray spectrum (1936–1942). His numerous postwar critical studies of the numerical values of the atomic constants, done in collaboration with E. Richard Cohen, remained the definitive work on the subject until a more precise measurement of h/e using the ac Josephson effect in superconductors (1969). led to a new set of values for the fundamental constants,

BIBLIOGRAPHY

I. Original Works. The starting point for the study of DuMond’s life and work is his unpublished “Autobiography of a Physicist.” 2 vols. (1972). copies of which are at the Center for History of Physics at the American Institute of Physics, and in the archives of the California Institute of Technology. Volume I includes a complete chronological list of more than 175 scientific papers DuMond wrote between 1915 and 1970. With E. Richard Cohen and K. M. Crowe, DuMond published Fundamental Constants of Physics (New York, 1957). On DuMond’s role as guardian of the constants, see his “Pilgrims” Progress in Search of the Fundamental Constants.’ in Physics Today. 18 (October 1965), 26–43.

Manuscript sources include extensive correspondence between DuMond and Millikan from 1934 to 1946, in the papers of Robert A. Millikan: between DuMond and DuBirdge from 1946 to 1966, in the papers of Lee A. DuBirdge: and nine boxes of correspondence and reprints, all in the archives of the California Institute of Technology. Another 157 letters are in the papers of Raymond T. Birge in the Bancroft Library at Berkeley.

II. Secondary Literature. W.K.H. Pansofsky, DuMond’s son-in-law, reviewed his career, treating also DuMonds World War II contributions and inventions, in Biographical Memoirs. National Academy ol Sciences, 52 (1980). 160–201, with portrait and bibliography. Short obituary notices include E. Richard Cohen, “Jesse W. M. DuMond”s in Physics lodaw 30 (March 1977). 74–75: F. Boehm, “Jesse W. M. DuMond. 1892–1976,” in Engineering and Science, 40 (March-April 1977), 35–36. On the X-ray determination of the electron charge and Millikans value of e, see R. H. Kargon, The Rise of Robert Millikan: Portrait of a Life in American Science (Ithaca. N.Y., 1982). chap. 6 On the ac Josephson effect and the physical constants, the classic paper is B. N. Taylor. W. H. Parker, and D. N. Langenberg. “Determination of e/h Using Macroscopic Quantum Phase Coherence in Superconductors; Implications for Quantum Electrodynamics and the fundamental Phssical Constants,” in Review of Modem Physics. 41 (1969). 375–496.

Judith R. Goodstein