Hendrik Anthony Kramers (17.12.1894 —24.04.1952) was a Dutch theoretical physicist. He was born in Rotterdam. He graduated from the University of Leiden (1916). In 1920-26 he worked at the Institute of Theoretical Physics in Copenhagen, in 1926 —34 he was professor at the University of Utrecht and from 1934 at Leiden.
His research was in the fields of atomic physics, quantum mechanics, solid-state physics, magnetism, physical optics, the kinetic theory of gases and low-temperature physics. In 1920, on the basis of Bohr's correspondence principle, he gave a theory of the Stark effect. Kramers's work on the helium atom was of great importance for quantum theory. In 1924 he predicted negative dispersion, and in 1925 he obtained the complete dispersion formula, which includes Raman scattering (the Kramers–Heisenberg dispersion formula). In 1924, together with N. Bohr, J. Slater and others, he put forward the idea that in atomic processes energy and momentum are conserved only statistically. This idea, however, was soon recognised to be mistaken.
He took part in the development of the mathematical formalism of quantum mechanics. In 1926, independently of L. Brillouin and G. Wentzel, he proposed a method of finding the approximate eigenfunctions of the one-dimensional Schrödinger equation which establishes a connection with the old Bohr–Sommerfeld quantisation rules (the Brillouin–Wentzel–Kramers, or WKB, method). He developed the formalism of the theory of the multiplet structure of spectra. In 1927, independently of R. Kronig, he formulated the dispersion relations in classical electrodynamics (the Kramers–Kronig relations). In 1929 he formulated a theorem of great importance for the problem of magnetism (Kramers's theorem). In 1934 he developed the theory of indirect exchange interaction for non-metallic compounds, introducing the superexchange mechanism. In 1937 he developed Dirac's hole theory. He put forward the idea of charge conjugation as a general symmetry property of fermions. He was the first to point out (1938) the need for the correct subtraction of infinite quantities in quantum electrodynamics.
In 1946 —50 he was president of the International Union of Pure and Applied Physics. The H. Lorentz (1948) and D. Hughes (1951) Medals.