Frédéric Joliot-Curie (19.03.1900-14.08.1958) was a French physicist and a member of the Paris Academy of Sciences (1943). He was born in Paris. In 1923 he graduated from the School of Physics and Chemistry (Paris). In 1925 — 30 he worked at the Radium Institute and at the same time taught at various educational institutions in Paris. It was at the Radium Institute that his joint work began with I. Curie, whom he married in 1926. In 1928 their joint papers begin to appear, signed from 1934 “Joliot-Curie”. In 1930 he defended his doctoral thesis and became a research fellow of the National Science Fund, and from 1932 he also taught at the Sorbonne. From 1937 he was professor at the Collège de France and at the same time head of the laboratory of atomic synthesis at the National Centre for Scientific Research (director in 1944—45). In 1946—50 he was High Commissioner of the Commissariat for Atomic Energy, which was set up on his initiative. In this post he did much for the development of atomic science and engineering in France and for the organisation of centres of nuclear physics. In May 1950 the French government removed Joliot-Curie from the leadership of the Commissariat because he refused to carry out nuclear research for military purposes. From 1956 he was also professor at the University of Paris, head of the Curie laboratory at the Radium Institute and director of the Institute of Nuclear Physics at Orsay.
His research concerned nuclear physics, nuclear chemistry and nuclear engineering. Together with Irène Curie he began in 1928 a systematic study of the nuclear reactions produced by alpha particles irradiating light nuclei, using for this the most powerful alpha-particle source of the time, a polonium preparation of 200 millicuries. With an improved Wilson cloud chamber they observed the decay of individual atoms and studied the phenomena caused by the passage of alpha particles through matter. Reproducing, with some changes, the Bothe — Becker experiments known at the time in order to obtain the so-called beryllium radiation, the Joliot-Curies found that this new radiation was able to knock the nuclei out of the atoms of the substance through which it passed. They demonstrated this knocking out of nuclei by photographing with a Wilson cloud chamber the tracks formed by the ejected nuclei of hydrogen, helium and nitrogen. Starting from the Joliot-Curies' experiments and altering them somewhat, J. Chadwick showed that the radiation responsible for knocking out the nuclei is a stream of neutral particles — neutrons. So the riddle of the beryllium radiation was solved, and the experiments of F. and I. Joliot-Curie played the decisive part in it.
In his later work he studied the properties of neutrons and the various types of nuclear reaction in which neutrons are formed. In 1934 he showed that the mass of the neutron is somewhat greater than that of the proton, which pointed to the instability of the neutron. Frédéric and Irène Joliot-Curie were the first, in 1933, to obtain a photograph with the tracks of an electron and a positron created by a gamma quantum (pair production), and in the same year F. Joliot-Curie, together with J. Thibaud, was the first to observe the annihilation of electrons and positrons.
In 1934 the Joliot-Curies discovered the phenomenon of artificial radioactivity induced by fast alpha particles (Nobel Prize in Chemistry, 1935) and obtained a number of artificial radioactive isotopes; they discovered a new type of radioactivity, the positron type. F. and I. Joliot-Curie predicted that artificial radioactivity could also be induced by neutrons, deuterons and protons.
Almost at the same time as O. Hahn and F. Strassmann, F. Joliot-Curie discovered experimentally the fission of uranium by neutrons, and he was one of the first to conclude that the fission of uranium nuclei into fragments must be accompanied by the appearance of new neutrons; he calculated (May 1939) the number of secondary neutrons emitted. At that time F. Joliot-Curie also saw the possibility of a chain nuclear reaction developing in uranium, releasing an enormous amount of energy in an explosion. In 1939—40 he drew up a number of engineering designs for the release of nuclear energy.
In 1939, with his colleagues, he began work on the construction of a heavy-water nuclear reactor. The first measurements were made of the effective cross-section for the capture of thermal neutrons by deuterium nuclei. In May 1940, however, this research was broken off by the occupation of France by the fascist invaders (1940—44). His closest assistants, H. Halban and L. Kowarski, took the documentation and the stock of heavy water out to England, while Joliot-Curie himself stayed in occupied France, where he used his knowledge to fight the occupiers: explosives were made in his laboratory at the Collège de France. He was a member of the Resistance and headed the National Front organisation. After the war he resumed and extended his nuclear research. As early as the beginning of 1948 he started up the first French cyclotron, and in December 1948 an experimental heavy-water nuclear reactor.
F. Joliot-Curie was an outstanding public figure and a member of the French Communist Party (from 1942). From 1950 he was chairman of the World Peace Council, and in 1950 he initiated the Stockholm Appeal. For his work in defence of peace he was awarded in 1951 the International Lenin Prize “For Strengthening Peace Among Peoples”. From 1947 he was president of the France — USSR society, and he was one of the founders and, from 1946, the president of the World Federation of Scientific Workers. President of the French Physico-Chemical Society (1936 — 38).
A member of many academies of sciences and scientific societies, including a foreign member of the USSR Academy of Sciences (1947). The P. Curie (1923), C. Matteucci (1932), D. Hughes (1947) and A. Lavoisier (1954) Medals.