Hans Kramers

Hans Kramers
Hans Kramers in c. 1928
Born	Hendrik Anthony Kramers (1894-02-02)2 February 1894 Rotterdam, Netherlands
Died	24 April 1952(1952-04-24) (aged 58) Oegstgeest, Netherlands
Nationality	Dutch
Fields	Physics
Alma mater	Leiden University
Doctoral advisor	Niels Bohr Paul Ehrenfest
Doctoral students	Henri Brinkman Dirk ter Haar Lamek Hulthén Nico van Kampen Jacob Kistemaker Tjalling Koopmans Luitzen Johannes Oosterhoff
Known for	Kramers–Heisenberg formula Wentzel–Kramers–Brillouin approximation Kramers–Kronig relations Kramers–Wannier duality Kramers model for polymer chains Kramers–Anderson superexchange Kramers' degeneracy theorem Kramers' law Kramers' opacity law
Notable awards	Lorentz Medal (1947) Hughes Medal (1951)

Hendrik Anthony "Hans" Kramers (2 February 1894 – 24 April 1952) was a Dutch physicist who worked with Niels Bohr to understand how electromagnetic waves interact with matter.

Hans Kramers was born in Rotterdam. the son of Hendrik Kramers, a physician, and Jeanne Susanne Breukelman.

In 1912 Hans finished secondary education (HBS) in Rotterdam, and studied mathematics and physics at the University of Leiden, where he obtained a master's degree in 1916. Kramers wanted to obtain foreign experience during his doctoral research, but his first choice of supervisor, Max Born in Göttingen, was not reachable because of the first world war. Because Denmark was neutral in this war, as was the Netherlands, he travelled (by ship, overland was impossible) to Copenhagen, where he visited unannounced the then still relatively unknown Niels Bohr. Bohr took him on as a Ph.D. candidate and Kramers prepared his dissertation under Bohr's direction. Although Kramers did most of his doctoral research (on intensities of atomic transitions) in Copenhagen, he obtained his formal Ph.D. under Ehrenfest in Leiden, on 8 May 1919.

Kramers greatly enjoyed music and could play the cello and the piano.

After working for almost ten years in Bohr's group and becoming an associate professor at the University of Copenhagen, Kramers left Denmark in 1926 and returned to the Netherlands. He became a full professor in theoretical physics at Utrecht University, where he supervised Tjalling Koopmans. In 1934 he left Utrecht and succeeded Paul Ehrenfest in Leiden. From 1931 until his death he held also a cross appointment at Delft University of Technology.