Kleppner, Daniel (1932– )

US physicist. In 1960 he helped develop the first hydrogen maser clock, an instrument 100,000 times more accurate than any atomic clock previously constructed. He continued research with atomic hydrogen, utilized lasers to examine dimagnetic spectra or atoms, and made quantum electrodynamic investigations of atomic structures. He taught and performed research at Harvard University (1959–66) and at the Massachusetts Institute of Technology (from 1966). Kleppner was born in New York City.