MANDELSHTAM, LEONID ISAAKOVICH

(b. Mogilev, Russia, 5 May 1879; d. Moscow, U.S.S.R., 27 November 1944)

physics.

Mandelshtam’s father, Isaak Grigorievich Mandelshtam, was a physician widely known in southern Russia. His mother, Minna Lvovna Kahn, was her husband’s second cousin, knew several foreign languages, and was an outstanding pianist. Mandelshtam’s uncles, the biologist A. G. Gurvich and the distinguished specialist in petroleum chemistry L. G. Gurvich, greatly influenced his upbringing. Soon after his birth the family moved to Odessa, where Mandelshtam passed his childhood and youth. After graduating from the Gymnasium with honors in 1897, he entered the mathematical section of the Faculty of Physics and Mathematics of Novorossysk University in Odessa; two years later he was expelled for having participated in antigovernment student riots.

He continued his education at the Faculty of Physics and Mathematics of Strasbourg University, where Ferdinand Braun soon attracted him to scientific research in his own laboratory—primarily questions of electromagnetic vibration and their application to radiotelegraphy. In 1902 Mandelshtam defended his dissertation for the doctorate of natural philosophy at Strasbourg University, with highest distinction. He then became Braun’s extra-staff personal assistant and, in 1903, his second staff assistant at the Strasbourg Physical Institute. Mandelshtam’s friendship and collaboration with the distinguished Russian radiophysicist Nikolay Dmitrievich Papaleksi, which continued until his death, began at this time.

In 1907 Mandelshtam married Lidya Solomonovna Isakovich, the first Russian woman architect. In 1914, just before the beginning of World War I, Mandelshtam returned to Russia with his family and Papaleksi. After working as privatdocent in physics at Novorossysk University, in 1915 he became scientific consultant at the Petrograd radiotelegraph factory and, in 1917, professor of physics ant the Polytechnical Institute in Tiflis. From 1918 to 1921 he was scientific consultant of the Central Radio Laboratory in Moscow and later in Petrograd. In 1925 he was appointed professor of theoretical physics at Moscow State University. He settled in Moscow, where he began his long collaboration with the prominent Soviet physicist G. S. Landsberg. In 1928 Mandelshtam was elected a corresponding member of the Academy of Sciences of the U.S.S.R. and in 1929 an active member. From the fall of 1934 Mandelshtam took an active part in the work of the P. N. Lebedev Physical Institute of the Academy of Sciences in Moscow, in addition to his work at the university. Because of serious heart disease Mandelshtam was evacuated during World War II to Borovoye in Kazakhstan, where he continued his theoretical work. After the war he returned to Moscow and spent the rest of his life at Moscow State University and the Lebedev Physical Institute.

Mandelshtam’s scientific research, which embraced extremely varied areas of physics and its practical applications, centered fundamentally on optics and radiophysics. His accomplishments in optics include the discovery of the phenomenon of combination scattering, the study of the effect of the fluctuation scattering of light in a uniform medium, and the theory of the microscope. In an early work (1907) Mandelshtam was the first to show that the scattering of light observed in a uniform medium was caused not by the presence of movement among the molecules, as Rayleigh had asserted, but by the occurrence of irregularities connected, according to Smoluchowski’s idea, with the fluctuations of density caused by random heat motion.

In 1918 Mandelshtam proposed the idea that the Rayleigh lines must reveal a fine structure, caused by the scattering of light on adiabatic fluctuations. His work on this question did not appear until 1926, after the publication of an analogous idea of Brillouin. The Mandelshtam-Brillouin effect was first experimentally demonstrated by Mandelshtam and Landsberg in 1930 in crystals and by E. F. Gross in liquids. During this research Mandelshtam and Landsberg discovered in 1928 an essentially new effect in crystals, combination scattering, which consists of a regular variation in the frequency of light scattering. An analogous effect was discovered at the same time in liquids by the Indian physicists C. V. Raman and K. S. Krishnan. A preliminary communication of the discovery of the Indian scientists appeared in print a few months before the communication of Mandelshtam and Landsberg. The effect, known in the Soviet Union as combination scattering, is elsewhere called the Raman effect. The study of these phenomena led Mandelshtam to the discovery and investigation of light scattering in fluctuations originating on the surface of a liquid.

In radiophysics and its applications Mandelshtam’s research with Papaleksi on nonlinear vibrations and the creation of radiogeodesy is of especially great significance. Begun in 1918, their research on nonlinear vibrations led to results obtained in the 1930’s in the formulation of so-called conditions of discontinuity, which are the basis of “explosive” vibrations and led to the development of the theory of multivibrators. The subsequent discovery of the conditions of appearance of n-type resonance made it possible to stimulate vibrations in a circuit, the frequencies of which are precisely n times lower than the frequencies of external electromotive forces. Associated with this work is the research on vibrations in linear systems with parameters changing through time. In 1931 Mandelshtam and Papaleksi constructed the first alternating-current parametrical generator with periodically changing inductivity. One of their most distinguished achievements was the radiointerference method of precise measurement invented in 1938 (radiogeodesy), which was also the most precise method of measuring the velocity of propagation of radio waves. In conjunction with studies in optics and radiophysics, Mandelshtam also conducted theoretical research on the basic problems of quantum mechanics. An outstanding lecturer who loved teaching, Mandelshtam taught a large school of physicists, including a number of distinguished scientists (I. E. Tamm, M. A. Leontovich, A. A. Andronov, S. E. Khaikin, among others).

BIBLIOGRAPHY

Mandelshtam’s complete collected works were published as Polnoe sobranie trudov, S. M. Rytov and M. A. Leontovich, eds., 5 vols. (Leningrad, 1947–1955). A biographical sketch by N. D. Papaleksi is in I, 7–66. See also N. D. Papaleksi, “Kratky ocherk zhizni i nauchnoy deyatelnosti Leonida Isaakovicha Mandelshtama,” in Uspekhi fizicheskikh nauk, 27 no. 2 (1945), 143–158, a short sketch of Mandelshtam’s life and scientific work.

J. Dorfman