Nikolay Semyonov
Nikolay Semyonov, a physicist and chemist, and a leader of the Soviet nuclear weapons programme, was born on 15th April, 1896, and died on 25th September, 1986 in Moscow. His primary scientific contributions are related to the quantitative theory of chemical chain reactions, the theory of thermal explosion, and the burning of gaseous mixtures.
He was a Physics graduate of Petrograd (St Petersburg) University, and in 1920 he was put in charge of the electron phenomena laboratory of the Physico-Technical Institute in Petrograd. It was at this time, while working with Pyotr Kapitsa, that he discovered a way to measure the magnetic field of an atomic nucleus. In 1931, he became Director of the Institute of Chemical Physics of the USSR Academy of Sciences, and from 1944 he was a professor at the Moscow State University.
For his work on the mechanism of chemical transformation, he was awarded the 1956 Nobel Prize for Chemistry. Semyonov's work on the mechanism of chemical transformation includes an important analysis of the application of the chain theory (a sequence of reactions where a reactive product or by-product causes additional reactions) to different reactions, particularly combustion processes.
In chemistry and physics, a chain reaction is a reaction that, once started, continues without further outside influence. Proper conditions for a chain reaction depend not only on various external factors, such as temperature, but also on the quantity and shape of the substance in the reaction. A chain reaction can be of various types, but nuclear chain reactions are the best known, and it was in this particular area that Semvonov contributed his expertise to the nuclear weapons programme. He also made valuable contributions to the field of molecular physics and electron phenomena.
Semvonov published his work in three important books. The first was Chemistry of the Electron, published in 1927. This was followed by Chemical Kinetics and Chain Reactions in 1934, which was the first book in the USSR to propose a theory of chain reactions in chemistry. Further studies in chemical kinetics led to the publication, in 1954, of Some Problems of Chemical Kinetics and Reactivity, which was translated into many languages.
Semvonov received many awards and honours in his lifetime, including five Orders of Lenin. He was a member of the Chemical Society in London, Foreign Member of the Royal Society and Foreign Member of the American, Indian, German, and Hungarian Academies of Sciences. He held honorary doctorates from the University of Oxford and Brussels University.