He then was an Instructor in physics at Frankfurt and at
Stuttgart for one semester each. From fall 1929 to fall 1933 his headquarters
were the University of Munich where he became Privatdozent in May 1930. During
this time he had a travel fellowship of the International Education Board to go
to Cambridge, England, in the fall of 1930, and to Rome in the spring terms of
1931 and 1932. In the winter semester of 1932-1933,he held a position as Acting
Assistant Professor at the University of Tubingen which he lost due to the
advent of the Nazi regime in Germany.
Bethe emigrated to England in October 1933 where he held a temporary position as
Lecturer at the University of Manchester for the year 1933-1934, and a
fellowship at the University of Bristol in the fall of 1934. In February 1935 he
was appointed Assistant Professor at Cornell University, Ithaca, N. Y. U.S.A.,
then promoted to Professor in the summer of 1937. He has stayed there ever
since, except for sabbatical leaves and for an absence during World War II. His
war work took him first to the Radiation Laboratory at the Massachusetts
Institute of Technology, working on microwave radar, and then to the Los Alamos
Scientific Laboratory which was engaged in assembling the first atomic bomb. He
returned to Los Alamos for half a year in 1952. Two of his sabbatical leaves
were spent at Columbia University, one at the University of Cambridge, and one
at CERN and Copenhagen.
Bethe's main work is concerned with the theory of atomic nuclei. Together with
Peierls, he developed a theory of the deuteron in 1934 which he extended in
1949. He resolved some contradictions in the nuclear mass scale in 1935. He
studied the theory of nuclear reactions in 1935-1938, predicting many reaction
cross sections. In connection with this work, he developed Bohr's theory of the
compound nucleus in a more quantitative fashion. This work and also the existing
knowledge on nuclear theory and experimental results, was summarized in three
articles in the Reviews of Modern Physics which for many years served as
a textbook for nuclear physicists.
His work on nuclear reactions led Bethe to the discovery of the reactions which
supply the energy in the stars. The most important nuclear reaction in the
brilliant stars is the carbon-nitrogen cycle, while the sun and fainter stars
use mostly the proton-proton reaction. Bethe's main achievement in this
connection was the exclusion of other possible nuclear reactions. The Nobel
Prize was given for this work, as well as his work on nuclear reactions in
In 1955 Bethe returned to the theory of nuclei, emphasizing a different phase.
He has worked since then on the theory of nuclear matter whose aim it is to
explain the properties of atomic nuclei in terms of the forces acting between
Before his work on nuclear physics, Bethe's main attention was given to atomic
physics and collision theory. On the former subject, he wrote a review article
in Handbuch der Physik in which he filled in the gaps of the existing
knowledge, and which is still up-to-date. In collision theory, he developed a
simple and powerful theory of inelastic collisions between fast particles and
atoms which he has used to determine the stopping power of matter for fast
charged particles, thus providing a tool to nuclear physicists. Turning to more
energetic collisions, he calculated with Heitler the bremsstrahlung emitted by
relativistic electrons, and the production of electron pairs by high energy
Bethe also did some work on solid-state theory. He discussed the splitting of
atomic energy levels when an atom is inserted into a crystal, he did some work
on the theory of metals, and especially he developed a theory of the order and
disorder in alloys.
In 1947, Bethe was the first to explain the Lamb-shift in the hydrogen spectrum,
and he thus laid the foundation for the modern development of quantum
electrodynamics. Later on, he worked with a large number of collaborators on the
scattering of pi mesons and on their production by electromagnetic radiation.
Bethe is married to the daughter of P.P. Ewald, the well-known X-ray physicist.
They have two children, Henry and Monica.