Landsberg, Grigory Samuilovich

(b. Vologda, Russia, 22 January 1890; d. Moscow, U.S.S.R., 2 February 1957)

physics.

Landsberg’s father was a civil servant in a state forest preserve. The family first lived in Vologda, and then moved to Nizhniy Novgorod (now Gorky), where Landsberg graduated from the Gymnasium with a gold medal. In 1908 he entered the natural sciences section of the department of physics and mathematics of Moscow University, and after a year transferred to the mathematical section. He graduated in 1913 with a diploma of the first degree and remained at the university to prepare for a teaching career.

From 1913 to 1915 Landsberg was an assistnt at the university; in 1915 he published with N. N. Andreev his first scientific work, on the manufacture of large electrical resistors. From 1918 to 1920 he was docent at Omsk Agricultural Institute.

In 1920 he returned to Moscow and became a scientific co-worker at the Institute of Physics and Biophysics. his interest in optics dates from this time. In 1925 L. I. Mandelshtam transferred to Moscow University, and from this time on Landsberg and Mandelshtam conducted joint research. Their first study was on Rayleigh scattering crystals. A problem resulted from the presence in the crystals of internal defects, which caused an additional effect in the scattering of light. Using the fact that the intensity of the molecular scattering of light depends on temperature, Landsberg was able to separate the molecular scattering from the side effects. Landsberg and Mandelshtam subsequently began to study the spectral composition of light scattered by quart crystal. It followed from theoretical considerations that a fine structure must be present in the scattered light, caused by the modulation of the Rayleigh line by heat waves distributed through the crystal.

In the fall of 1927 Landsberg and Mandelshtam discovered a new phenomenon: satellites were observed in the spectrum of scattered light from a crystal; but the changes in their wavelength from the primary light appeared considerably larger than those expected from the modulation by heat waves. It became obvious that these changes were caused by the modulation of light by the infrared vibrations of the molecules of the crystal. The new phenomenon was called"combination scattering,” On 6 May 1928the first communication on this discovery was submitted for publication; It contained not only experimental facts but also the theory of the new effect and collection of experimental and computational data.

An analogous effect in liquids had been discovered simultaneously by C. V. Raman, who reported his discovery several weeks before Landsberg and Mandelshtam. Raman received the 1930 Nobel Prize in Physics for his discovery, and the effect was named after him. After careful study of the new effect Landsberg and Mandelshtam continued their research on Rayleigh scatterin gin crystals, concentratingon the intensity and anisotrophy of the light scattering Through this research an incomplete theory was clarified, and under Landsberg’s leadershp a new theory was worked out. In 1931 landsberg and Mandelshtam discovered a sharp intensification of the scattering near resonant spectral lines of atoms.

In 1932 Landsberg was elected corresponding member of the U.S.S.R. Academy of sciences. His broad research in the area of emission spectral analysis and its applications began a this time. Landsberg and his co—workers developed a method of rapid identification of alloyed steels by spectral analysis. In 1934 Landsberg organized a large scientific research laboratory in the Lebede Physical Institute of the U.S.S.R. Academy of Science; there Landsberg and his colleagues carried out investigation on combination scattering in organic substances, which permitted them to clarify a number of peculiarities in the hydrogen bond and the conditions of formation of associated complexes. Landsberg’s development of methods and devices for spectral analysis played a considerable practical rol during World War II, when Landsberg worked in Kazan, In 1940 Landsberg was awarded the Stage Prize for his work on spectral analysis, and in 1946 he was elected an active member of the U.S.S.R. Academy of Sciences. He subsequently carried out investigations of molecular scatting in viscous liquids and amorphous bodies.

Landsberg gave considerable attention to the teaching of physics. In 1929 with B. A. Vvedensky he wrote Sovremennoe uchenic of magnetizeme (“Contemporary Thoery of Mangetism”). In 1934 he published a basis course, Optiki (“Optics”), still widely used in Soviet higher educational institutions. On his initiative the three—volume Elementarny uchebnik fiziki (“Elementary Textbook of Physics”) was created; it has been reprinted many times.

BIBLIOGRAPHY

Landsberg’s selected works were published in Moscow in 1958. See See Uspekhi fixicheskikh nauk63 , no. 2 (Oct. 1957), a commemorative issue that includes recollections of Landsberg by I. B. Tamm, pp. 287–288; a short sketch of his life and work by S. L. Madelshtam, pp. 289–299; and a portait by V. A. Fabrikant of Landsberg as author and editor of physics textbooks, pp. 455–460.

J. G. Dorfman