Solomon Isaakovich Pekar (born 16.03.1917) is a Soviet theoretical physicist and an academician of the Academy of Sciences of the Ukrainian SSR (1961). He was born in Kiev. He graduated from Kiev University (1938). In 1938-60 he worked at the Institute of Physics of the Academy of Sciences of the Ukrainian SSR (head of a department from 1944), and from 1960 he has been head of the department of theoretical physics at the Institute of Semiconductors of the Academy of Sciences of the Ukrainian SSR; from 1944 he has also been professor at Kiev University.
His work was in solid-state theory. He developed (1939) a quantitative theory of barrier-layer rectifiers. He introduced (1946) the concept of polarons and developed (1946—49) their theory. He proposed a number of methods and approaches important for solid-state theory. He substantiated (1946) the method of the effective mass of the electron in a crystal and developed (1947 — 53) the theory of impurity electron centres and a general theory of the shape and temperature dependence of the bands of impurity absorption of light and of luminescence caused by electron-phonon interaction. He introduced the concept of the deformation potential (1951). He carried out a series of studies on the theory of excitons, predicted (1957) additional light waves in crystals in the region of exciton absorption and constructed (1957 — 60) a new crystal optics. He proposed (1964) a special mechanism of electron-phonon coupling and, on its basis, a theory of the amplification of ultrasound by the drift of current carriers. He predicted (1969) the possibility of a self-stimulated chemiluminescent reaction in gases and developed a theory of its use in chemical lasers. He obtained (1975) an expression for the energy of an electromagnetic field of arbitrary time dependence in a medium with frequency and spatial dispersion.
State Prize of the Ukrainian SSR (1981). He created a school of physicists (M. F. Deigen, M. A. Krivoglaz, Yu. E. Perlin, K. B. Tolpygo, I. M. Dykman, E. I. Rashba and others).