Walther Bothe
was born on January 8, 1891, at Oranienburg, near Berlin.
From 1908
until 1912 he studied physics at the University of Berlin, where he was a pupil
of Max Planck, obtaining his doctorate just before the outbreak of the 1914-1918
war. From 1913 until 1930 he worked at the Physikalisch-Technische Reichsanstalt
in the same city, becoming a Professor Extraordinary in the University there.
In 1930 he was appointed Professor of Physics, and Director of the Institute of
Physics at the University of Giessen.
In 1932 he was appointed Director
of the Institute of Physics at the University of Heidelberg, in succession to
Philipp Lenard, becoming in 1934 Director of the Institute of Physics at the Max
Planck Institute for Medical Research in that city. At the end of the Second World
War, when this Institute was taken over for other purposes, Bothe returned to
the Department of Physics in the University, where he taught until the illness
which had handicapped him for several years compelled him to restrict the scope
of his work. He was able, however, to supervise the work of the Institute of Physics
in the Max Planck Institute and he continued to do this until his death in Heidelberg
on February 8, 1957.
Bothe's scientific work coincided with the opening
up of the vast field of nuclear physics and the results he obtained led to new
outlooks and methods.
He was, during the First World War, taken prisoner
by the Russians and spent a year in captivity in Siberia. This year he devoted
to mathematical studies and to learning the Russian language; in 1920 he was sent
back to Germany.
He then collaborated with H. Geiger at the Physikalisch-Technische
Reichsanstalt in Berlin. Together with Geiger, whose influence determined much
of his scientific work, he published, in 1924, his method of coincidence, by which
important discoveries were subsequently made. It is based on the fact that, when
a single particle passes through two or more Geiger counters, the pulses from
each counter are practically coincident in time. The pulse from each counter is
then sent to a coincidence circuit which indicates pulses that are coincident
in time. Arrays of Geiger counters in coincidence select particles moving in a
given direction and the method can be used, for example, to measure the angular
distribution of cosmic rays. Bothe applied this method to the study of the Compton
effect and to other problems of physics. Together he and Geiger clarified ideas
about the small angle scattering of light rays and Bothe summarized their work
on this problem in his Handbuch article published in 1926 and 1933, establishing
the foundations of modern methods for the analysis of scatter processes. From
1923 until 1926 Bothe concentrated, especially on experimental and theoretical
work on the corpuscular theory of light. He had, some months before the discovery
of the Compton effect, observed, in a Wilson chamber filled with hydrogen, the
short track of the recoil electrons of X-rays and he did further work on the direction
of the emission of photo electrons. Together he and Geiger related the Compton
effect to the theory of Bohr, Kramers, and Slater, and the results of their work
provided strong support for the corpuscular theory of light.
In 1927
Bothe further clarified, by means of his coincidence method, ideas about light
quanta in a paper on light quanta and interference.
In the same year
he began to study the transformation of light elements by bombardment with alpha
rays. The resulting fission products had, until then, been seen by the eye only
as scintillations, but Bothe, in collaboration with Fränz, made it possible
to count them by means of their needle counter.
In 1929, in collaboration
with W. Kolhörster, Bothe introduced a new method for the study of cosmic
and ultraviolet rays by passing them through suitably arranged Geiger counters,
and by this method demonstrated the presence of penetrating charged particles
in the rays, and defined the paths of individual rays.
For his discovery
of the method of coincidence and the discoveries subsequently made by it, which
laid the foundations of nuclear spectroscopy, Bothe was awarded, jointly with
Max Born, the Nobel Prize for Physics for 1954.
In 1930 Bothe, in
collaboration with H. Becker, bombarded beryllium of mass 9 (and also boron and
lithium) with alpha rays derived from polonium, and obtained a new form of radiation
that was even more penetrating than the hardest gamma rays derived from radium,
and this led to the discovery of the neutron, made by Sir James Chadwick in 1932.
At Heidelberg, Bothe was able, after much diffculty, to obtain the money
necessary for building a cyclotron. He worked, during the 1939-1945 war, on the
diffusion theory of neutrons and on measurements related to these.
In June 1940 he published his Atlas of Cloud-Chamber Figures.
He was a member of the Academies of Sciences of Heidelberg and Göttingen,
and a Corresponding Member of the Saxon Academy of Sciences, Leipzig. He was awarded
the Max Planck Medal and the Grand Cross of the Order for Federal Services. In
1952, he was made a Knight of the Order of Merit for Science and the Arts.
Bothe's remarkable gifts were not restricted to physics. He had an astonishing
gift of concentration and his habit of carefully making the best use of his time
enabled him to work at great speed. In the laboratory he was often a difficult
and strict master, at his best in discussions in small classes there, but in the
evenings at home he was, with his Russian wife, very hospitable and all the difficulties
of the day were then forgotten.
To his hobbies and recreations he
gave the same concentration and intensity of effort that he gave to his scientific
work. Chief among them were music and painting. He went to many musical concerts
and himself played the piano, being especially fond of Bach and Beethoven. During
his holidays he visited the mountains and did many paintings in oil and water
colour. In these his style was his own. He admired the French impressionists and
was eager and vigorous in his discussions of the merits and demerits of various
artists.
Bothe married Barbara Below of Moscow. Her death preceded
his by some years. They had two children.
From Nobel Lectures, Physics 1942-1962, Elsevier Publishing Company, Amsterdam, 1964
This autobiography/biography was written at the time of the award and later published in the book series Les Prix Nobel/Nobel Lectures. The information is sometimes updated with an addendum submitted by the Laureate. To cite this document, always state the source as shown above.
Walther Bothe died on February 8, 1957.
