John Hasbrouck Van Vleck
Van Vleck, John Hasbrouck (1899-1980) an American theoretical physicist, is known as the “father of modern magnetism” because of his research on the magnetic properties of atoms. Van Vleck shared the 1977 Nobel Prize in physics with American physicist Philip Warren Anderson and British physicist Nevill Mott.
Van Vleck was born in Middletown, Connecticut, in 1899. He graduated from the University of Wisconsin in 1920 with a bachelor's degree in physics, and earned a doctorate in theoretical physics from Harvard University in 1922. He served on the faculty of the University of Minnesota 1923 to 1928 and the University of Wisconsin from 1928 to 1934. He then returned to Harvard, where he remained until his retirement in 1969.
While at Minnesota, Van Vleck proposed the general theory of magnetic and electric susceptibilities in gases. He then began investigating how quantum mechanics applied to and explained various forms of magnetism. His findings were detailed in The Theory of Electric and Magnetic Susceptibilities (1932), which to this day remains a standard text in the field. Further research in the 1930's on the interaction of electrons demonstrated that the energy of electrons in a particle is altered by the presence of other particles. In 1932, Van Vleck also developed the crystal field theory, which used quantum mechanics to evaluate the relationship between electron and ion energy levels in crystals.
During World War II (1939–1945), Van Vleck served on a committee to determine the feasibility of constructing an atomic bomb. He also worked on radar development at the Radio Research Laboratory in Cambridge, Massachusetts. There he discovered that water molecules have a spectral absorption line near .5 inch (1.3 cm) wavelength. This discovery demonstrated that a proposed radar system, which would have operated near that wavelength, was impractical.