The Russian physicist and physical chemist Nikolai Nikolaevich Semenov (1896-1986) is famous for his experiments explaining chemical reactions by means of the mechanism of chain reactions.
Nikolai Semenov was born on April 15, 1896, in Saratov. He displayed a keen interest in the physical sciences by the time he was 16 and in 1913 entered the physics and mathematics department of the University of St. Petersburg (later Petrograd and now Leningrad). At the age of 20 he published his first paper on the collision of molecules and electrons. In 1917 he ended his studies at the University of Petrograd, obtained a position as physicist in the Siberian University of Tomsk and later, in 1920, returned to work for the next 11 years at the Petrograd (in 1924 Leningrad) Institute of Physics and Technology.
In 1928 Semenov became a professor at the Leningrad Polytechnical Institute and organized its physics and mathematics department. Three years later he was appointed scientific chief of the Institute of Physical Chemistry of the Soviet Academy of Sciences. In 1932 he was elected to full membership in the academy, and from 1957 to 1963 he was the academy's secretary of the division of the chemical sciences. In 1944 he was assigned to the University of Moscow, heading the department of chemical kinematics. He also was instrumental in launching scientific journals and organizing Soviet conferences on physical chemistry.
Semenov's scientific investigations dealt primarily with molecular physics and electronic phenomena, the mechanism of chemical transformations, and the propagation of explosive waves. He published in "The Oxidation of Phosphorus Vapor at Low Pressures" (1927) his discovery of branching reaction chains in chemical transformations having the character of an explosion. Semenov intensively continued his researches in chemical reactions involving the chain theory and published his results in Chemical Kinetics and Chain Reactions (1935) and in the exhaustive two-volume study Some Problems in Chemical Kinetics and Reactivity (1958-1959). For his contributions to reaction kinetics, Semenov was awarded the Nobel Prize in 1956, the first resident Soviet citizen to achieve this distinction.
Semenov also played an active role in his country's affairs. He first joined the Communist party of the Soviet Union in 1947, served as a deputy in the Supreme Soviet in 1958, 1962, and 1966, and in 1961 was elected an alternate member of the party's Central Committee. In the Soviet Union he fought for the liberty of experimentation for the scientist, freedom of expression for the artist, and "chain reactions of success" for humanity as a consequence of international scientific exchanges. In 1971, Semenov, along with thirteen other Soviet scientists, signed a cablegram letter to President Richard Nixon, expressing concern that the Federal murder trial of African American militant and philosophy teacher Angela Davis be conducted such that her life would be spared (she was a member of the Communist party). Nixon responded by inviting all the scientists to attend her trial. Semenov died in 1986.
Only scattered articles on Semenov have thus far appeared in English and Russian newspapers and journals. A brief biographical sketch of Semenov by Albert Parry is in George W. Simmonds, ed., Soviet Leaders (1967). Semenov's scientific contributions receive mention in the comprehensive work of V. N. Kondratev, Chemical Kinetics of Gas Reactions, translated by J. M. Crabtree and S. N. Carruthers (1964), and in Keith J. Laidler, Reaction Kinetics (1966).