physical chemist whose investigations of dipole moments, X rays, and light scattering in gases brought him the 1936 Nobel Prize for Chemistry.

After receiving his Ph.D. in physics from the University of Munich (1910), Debye taught physics at the universities of Zürich, Utrecht, Göttingen, and Leipzig before becoming director of the Kaiser Wilhelm Institute for Theoretical Physics at Berlin (1935). Two months before the German invasion of his native country (1940), he went to Ithaca, N.Y., to deliver a lecture at Cornell University and remained there until he retired as chemistry department chairman in 1950.

Debye's first important research, his dipole moment studies, advanced knowledge of the arrangement of atoms in molecules and of the distances between the atoms. In 1916 he showed that solid substances could be used in powdered form for X-ray study of their crystal structures, thus eliminating the difficult step of first preparing good crystals.

Two of his most significant achievements came in 1923 when he and Erich Hückel extended Svante Arrhenius' theory of the dissociation of the positively and negatively charged atoms (ions) of salts in solution, proving that the ionization is complete, not partial. That same year he described the Compton effect, which the American physicist Arthur Holly Compton had discovered shortly before.