Ralph Kronig

Ralph Kronig
Ralph de Laer Kronig (1904–1995)
Born	March 10, 1904 (1904-03-10) Dresden, Germany
Died	November 16, 1995 (1995-11-17) (aged 91) Zeist, Netherlands
Residence	United States Netherlands Germany
Citizenship	United States Germany
Nationality	German
Institutions	Columbia University TU Delft
Alma mater	Columbia University
Doctoral advisor	Albert Potter Wills
Other academic advisors	Wolfgang Pauli
Known for	Discovery of particle spin Kronig-Penney model Coster-Kronig transition Kramers–Kronig relations
Notable awards	Max Planck Medal (1962)

Ralph Kronig (March 10, 1904 – November 16, 1995) was a German American physicist. He is noted for the discovery of particle spin and for his theory of x-ray absorption spectroscopy. His theories include the Kronig–Penney model, the Coster–Kronig transition and the Kramers–Kronig relation.

Ralph Kronig (later Ralph de Laer Kronig) was born on 10 March 1904 to German parents (Harold Theodor Kronig, Augusta de Laer) in Dresden, Germany. He died in Zeist on 16 November 1995 at the age of 91. Kronig received his primary and high-school education in Dresden and went to New York City to study at Columbia University where he received his PhD in 1925 and subsequently became instructor (1925) and assistant professor (1927).

Early in Kronig's career he had encountered Paul Ehrenfest who, while visiting America in 1924, had advised the young physicist Ralph Kronig to revisit Europe. Kronig left for that continent later in 1924 and paid visits to the important centers for theoretical-physics research in Germany and Copenhagen. It was a time of great expansion in the development of quantum mechanics, and that development was taking place in Europe. Kronig was privileged to be a young, brilliant physicist in that glory-day of 20th century theoretical physics, which made it possible for him to live and work among the great physicists of that era (Bohr, Ehrenfest, Heisenberg, Pauli, Kramers).