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Japanese physicist. In 1935 he discovered the strong nuclear force that
binds protons and neutrons together in the atomic nucleus, and predicted
the existence of the subatomic particle called the meson. Nobel prize 1949. Yukawa was born and educated in Kyoto and spent his career at Kyoto University, becoming professor 1939 and director of the university's newly created Research Institute for Fundamental Physics from 1953. Yukawa's theory of nuclear forces postulated the existence of a nuclear 'exchange force' that counteracted the mutual repulsion of the protons and therefore held the nucleus together. He predicted that this exchange force would involve the transfer of a particle (the existence of which was then unknown), and calculated the range of the force and the mass of the hypothetical particle, which would be radioactive, with an extremely short half-life. The muon, or meson, discovered 1936, fitted part of the description, and the pion, or meson, discovered 1947, fitted all of it. In 1936 Yukawa predicted that a nucleus could absorb one of the innermost orbiting electrons and that this would be equivalent to emitting a positron. These innermost electrons belong to the K electron shell, and this process of electron absorption by the nucleus is known as K capture. |