Physicist, California Institute of Technology, 1921-1953; taught the advanced courses in mathematical and theoretical physics. First European-trained physicist to come to Caltech on a permanent basis; recruited by Robert A. Millikan in 1921, a mathematical physicist among the generation who laid foundation for modern atomic physics. Studied in Munich under Arnold Sommerfeld; early research in theory of electromagnetic waves, particularly theory of their diffraction. Studied quantum theory of atomic structure based on classical mechanics; applying quantum theory to optics; Bohr's form of quantum theory; development of quantum mechanics. Also interested in psychoanalysis, helped establish the Los Angeles Institute of Psychoanalysis.