Hans Kramers

Hendrik Anthony "Hans" Kramers (1894 to 1952) was a Dutch physicist who worked with Niels Bohr on how electromagnetic waves interact with matter and who made important contributions to quantum mechanics and statistical physics. Born in Rotterdam, he studied mathematics and physics at the University of Leiden, prepared his doctoral research in Copenhagen under Bohr, and took his formal doctorate under Paul Ehrenfest in Leiden in 1919. After almost ten years in Bohr group he became professor of theoretical physics at Utrecht University, where he supervised Tjalling Koopmans, and in 1934 succeeded Ehrenfest at Leiden. His name is attached to the Kramers-Kronig relations, which tie the real and imaginary parts of causal complex functions together, to the Kramers-Heisenberg dispersion formula, to the WKB method, to Kramers degeneracy theorem and to the Kramers turnover in thermally activated barrier crossing. He also helped found the Mathematisch Centrum in Amsterdam.