Chadwick, James

James Chadwick (20.10.1891-24.07.1974) — English experimental physicist, Fellow of the Royal Society (1927). Born in Bollington. Graduated from the universities of Manchester and Cambridge. In 1923 — 35 he taught at the University of Cambridge and was deputy director of the Cavendish Laboratory, in 1935—48 he was professor at the University of Liverpool, and in 1948 — 58 he was head of Gonville and Caius College of the University of Cambridge. His work was in radioactivity and nuclear physics. In 1914 he discovered the continuous energy spectrum of beta radiation. In 1920 he studied the scattering of alpha particles by the nuclei of platinum, silver and copper and measured the charges of the nuclei directly, which finally confirmed Rutherford's theory of the atom and the conclusion that the charge of the nucleus equals the atomic number of the element. In 1932, studying the radiation produced when beryllium is irradiated with alpha particles, he showed that it is a stream of electrically neutral particles, neutrons (Nobel Prize. 1935). He studied the artificial transmutation of elements under the action of alpha particles (together with E. Rutherford) and the formation of electron-positron pairs by gamma quanta (together with P. Blackett and G. Occhialini). In 1934, together with M. Goldhaber, he was the first to detect the splitting of a nucleus under the action of gamma quanta (the nuclear photoeffect): bombarding deuterons with gamma quanta of energy 2.62 MeV, they split the deuteron and predicted the beta decay of the neutron. His research also concerned the achievement of a nuclear fission chain reaction. He was one of the first to calculate the critical mass of uranium-235. A member of a number of academies of sciences. The D. Hughes (1932), Copley (1950), M. Faraday (1950) and B. Franklin (1951) Medals.