Joliot, Frédéric

(b. Paris, France, 19 March 1900; d. Paris, 14 Augest 1958)

nuclear physics.

Joliot’s father, Henri Joliot, took part in the Commune of Paris at the end of the Franco-Prussian War and was obliged to spend several years in Belgium to escape the subsequent repression. Upon returning to France he settled in Paris, where he became a well-to-do tradesman. He was an ardent fisherman and hunter, and a virtuoso performer on the hunting horn, an instrument for which he “composed numerous calls. Joliot’s mother, Émilie” Roederer, came from a petit bourgeois Alsatian Protestant family. She married Henri Joliot in 1879; Frédéric was the last of their six children. Raised in a completely nonreligious family, Joliot never attended any church and was a thoroughgoing atheist all his life. At the age of ten he became a boarder at the Lycée Lakanal, located in a southern suburb of paris but, following the death of his father and family financial difficulties, he transferred to the École Primaire Supérieure Lavoisier in paris. There he prepared for the entrance examination for the Ecole Superieure de Physique et de Chimie Industrielle of the City of Paris, to which he was admitted in 1920.

In this prestigious school, which ordinarily would have prepared him for a career in engineering, Joliot was introduced to basic science and scientific research pursued solely to satisfy the passion for knowledge, with no concern for practical application. The director of studies at the time was the physicist Paul Langevin, who had a decisive influence on Joliot; he oriented the young man not only toward scientific research but also toward a pacifist and socially conscious humanism that eventually led him to socialism. During these years at the École Supérieure de Physique et de Chimie Industrielle, where a large portion of the curriculum was devoted to laboratory work, Joliot developed his talents as an experimenter. He graduated first in his class, but after fifteen months of military service he was still undecided on a career. A summer job in a large steel mill in Luxembourg (1922) left a strong impression on him, and the value of his engineering degree from one of the most highly regarded of the grandes écoles assured him a brilliant position in industry; but he felt himself drawn to scientific research. He discussed his situation with Paul Langevin, who, recognizing his exceptional gifts and sensing his true aspirations, advised him to accept a stipend that Mme. Curie had at her disposal to pay for a personal assistant.

Joliot took this advice and began work at the Institut du Radium of the University of Paris in the spring of 1925, under the guidance of Mme. Curie. At first he undertook further studies in modern physical chemistry, particularly radioactivity, at the laboratory itself; he also took courses at the university that enabled him to earn his licence. At the same time he successfully concluded his first personal research, on the electrochemical properties of polonium. He presented the results of this work, in the course of which he displayed great skill in handling difficult techniques, in his doctoral thesis (defended in 1930).

When Joliot entered the Radium Institute, Mme. Curie’s elder daughter, Iréne, was already an assistant there. Brought in contact with her through his work, he was rapidly attracted by her remarkable personality, which was wholly different from his own. They were married in 1926 but for most of the time continued to work separately. Only in 1931 did they begin the four years’ close collaboration that so successfully united their complementary qualities.

Frédéric and Iréne Joliot-Curie had a daughter and a son, both of whom became distinguished scientists. Héléne Joliot (b. 1927), who, like her father, graduated first in her class from the Ecole Superieure de Physique et de Chimie Industrielle of Paris, became a researcher in nuclear physics. In 1949 she married a grandson of Paul Langevin, who likewise was engaged in research. Thus in the third generation there was to be a married couple each of whom was a research physicist working in the field opened by Pierre and Marie Curie through the discovery of radium and extended by Frédéric and Iréne Joliot-Curie through that of artificial radioactivity. Pierre Joliot (b. 1932) chose to specialize in biophysics. He too maintained the family tradition, for he and his scientist wife Anne both chose the same area of research.

After Joliot defended his thesis, no academic post was available at the Radium Institute and he had to consider leaving scientific research and taking a job as an engineer in industry. Fortunately for the advancement of science, Jean Perrin, who directed the Laboratory of Physical Chemistry, located near the Radium Institute, and who had already appreciated Joliot’s great abilities as a researcher, arranged for him to receive a scholarship from the Caisse Nationale des Sciences, whose creation by the government Perrin had only recently obtained.

This scholarship permitted Joliot to continue research and to select freely his area of study. First he assembled the equipment that would enable him to observe under the best possible conditions the ionizing radiations emitted directly or secondarily by radioactive substances. His training as an engineer enabled him to draw up the plans and supervise in detail the construction of a greatly improved Wilson chamber. This device, also called a cloud chamber, makes it possible to see and to photograph the trajectories of electrically charged particles passing through a gas saturated with water vapor: a sudden expansion produces a supersaturation and causes tiny droplets of water to condense around each of the ions formed along its trajectory by every charged particle (electron, proton, a particle, and so on). Joliot called the direct, detailed view of individual corpuscular phenomena provided by this apparatus “the most beautiful experience in the world,” and the cloud chamber was always his favorite tool of research. The one that he had constructed in 1931 could function at various pressures, from the low pressure of pure saturant water vapor at room temperature up to a pressure of several atmospheres. It had a diameter of about fifteen centimeters and could operate in a magnetic field of 1,500 gauss produced by large coils surrounding the cylindrical chamber in which the expansion took place. This arrangement permitted Joliot to determine the energy of the electronic rays (β rays) by measuring the curvature of their trajectories on the photographs. In addition Joliot set up devices to count the ionized particles detected by a thin-walled Geiger counter and an ionization chamber connected to an electrometer of high sensitivity. Finally, taking advantage of a large stock of radium D patiently accumulated at the Radium Institute by Mme. Curie, Joliot, in collaboration with his wife, prepared very strong sources of α rays emitted by polonium that had been deposited as thin layers possessing a high surface density of activity. The preparation of these sources was both difficult and dangerous because of the very high toxicity of polonium.

Joliot used all this equipment with a fertile imagination and a keen sense of those experiments which might lead to the observation of unexpected phenomena. In little more than two years of intense activity, alone or in collaboration with Irène Curie, he made a series of remarkable discoveries that culminated in the discovery of artificial radioactivity at the beginning of 1934. An enthusiastic innovator, Joliot constantly devised new experiments the significance of which was so immediately obvious that they always appeared extremely simple. The elegance of their conception and execution belied the laborious work with complex apparatus that had gone into their preparation.

The first experiment Joliot carried out with this equipment well demonstrates the manner in which he worked in order to increase his chances of observing unforeseen phenomena. He decided to study, in collaboration with Irène Curie, the strangely penetrating radiation emitted—as the German physicists W. Bothe and J. Becker had discovered in 1930—by certain light elements, notably beryllium and boron, when they are bombarded with αrays. The Joliot- Curies set up an intense source of this mysterious radiation by placing one of their very strong polonium preparations against a beryllium plate; and they used their highly sensitive ionization chamber to detect, after filtration through fifteen millimeters of lead, the penetrating radiation issuing from this source. Thinking that the ionization measured might be the result of easily absorbable secondary radiations produced in the wall of the ionization chamber by the very penetrating radiation (as was the case for γ rays) and wishing to be able to vary the nature of the last solid plates traversed by the radiation, they made the ultrapenetrating radiation enter the ionization chamber through a window covered by a sheet of aluminum only five microns thick; in front of this sheet they were able to interpose plates of various substances.

The analogy of the γ rays with ionizing secondary radiations may have suggested the use of a much thicker sheet of aluminum to cover the entrance window, but the more difficult option of an extremely thin sheet made possible the observation of secondary rays of very low penetrating power and thus permitted the Joliot-Curies to make an important discovery. With this arrangement they ascertained that interposing plates of most of the substances under examination (carbon, aluminum, copper, silver) between the source and the ionization chamber left the measured current virtually unaffected but that placing a screen made of a hydrogen-containing substance (paraffin, cellophane, water) in front of the window of the ionization chamber caused a large increase in the current. The secondary radiation responsible for this unexpected increase was completely absorbed by a sheet of aluminum 0.20 millimeter thick. It appeared that this radiation, produced only in hydrogen-containing substances, consisted of protons ejected by the penetrating Bothe-Becker radiation. This hypothesis was confirmed by various experiments that the Joliot-Curies reported when they announced the discovery of this surprising phenomenon in a note presented to the Academy of Sciences on 18 January 1932. A short time later they were in fact able to observe, with the aid of their Wilson chamber, the easily identifiable trajectories of the protons thus ejected and to prove, by filling their ionization chamber with helium, that the Bothe-Becket radiation also ejected helium nuclei (Comptes rendus . . . de l’Académie des sciences97 , 708 [22 Feb, 1932]).

Joliot would not have been able to make these unforeseen discoveries if he had closed his ionization chamber with a sheet of aluminum several tenths of a millimeter thick instead of making the effort required by the use of a foil a hundred times thinner. Analyzing the conditions of his success, he wrote in 1954: “I have always attached great importance to the manner in which an experiment is set up and conducted. It is, of course, necessary to start from a preconceived idea; but whenever it is possible, the experiment should be set up to open as many windows as possible on the unforeseen.”

Immediately following the Joliot-Curies’ first publication on this subject, the English physicist James Chadwick began to study the ejection of atomic nuclei by Bothe-Becker radiation. He employed a proportional pulse amplifier that allowed him to compare the energies of the ejected helium or nitrogen nuclei with that of the protons. He concluded that these ejections were the result of collisions between the nuclei and fast-moving uncharged particles that possessed a mass of the same order of magnitude as that of the protons and undoubtedly were torn from the nuclei of beryllium or boron by the α particles. Chadwick had discovered the neutrons; he published his results in Nature on 27 February 1932.

Joliot devoted the years 1932 and 1933 to studying, generally in collaboration with his wife, Bothe- Becker radiation and the phenomena accompanying its production. They proved that this radiation is complex, consisting not only of the neutronic rays that cause the ejection of light nuclei but also of γ rays of several million electron volts; when the latter pass through matter, they tear away electrons and eject them at high speeds.

The Joliot-Curies found that these high-energy γ rays also eject positive electrons—their existence had been predicted by Dirac and they had just been discovered in cosmic radiation by the American physicist C. D. Anderson. Furthermore, by operating their Wilson chamber in a magnetic field, they were able to make the first photographs of the creation of an electron pair (one positive and one negative) by materialization of a γ photon.

Resuming the study of radiation emitted by light elements bombarded by α particles, the Joliot-Curies discovered that when certain of these elements, notably boron and aluminum, are submitted to such bombardment there occurs an emission not only of protons or neutrons but also of positive electrons, the origin of which they attributed to some induced transmutations. They showed that the energies of the positive electrons created in this manner form a continuous spectrum analogous to that formed by the energies of the negative electrons emitted in β radioactivity, suggesting that the emission of a positive electron during transmutation is accompanied by that of a neutrino bearing a variable fraction of the available energy. In retrospect it seems that the observation of artificial radioactivity could have immediately followed this last discovery, which was presented and discussed in October 1933 at the Solvay Physics Conference, a gathering of the world’s greatest nuclear physicists. As a matter of fact, Joliot did not continue his research on the emission of positive electrons by aluminum bombarded by α particles until he had successfully completed, at the end of December 1933, a study of the annihilation of positive electrons stopped by matter, in which he proved—as Dirac had foreseen—that this annihilation is accompanied by the emission of two γ photons of approximately 500 KEV.

Resuming the earlier investigations of emission phenomena, Joliot covered the window of his cloud chamber with a thin sheet of aluminum foil, against which he placed a strong source of polonium. He was surprised to observe that the emission of positive electrons, induced by the polonium, continued for several minutes after it had been removed and, therefore, after all irradiation of the aluminum had ceased. Realizing the significance of this observation and the importance of rapidly deducing from it every possible consequence, Joliot called in his wife; he wanted her to take part in the experiments that had to be carried out immediately in order to furnish decisive proof of the creation of new radioelements. Their observations, repeated with a thin-walled Geiger counter, confirmed that radioactive atoms with a halflife of a little more than three minutes are formed in aluminum irradiated by α rays. The radioactivity was analogous to the β radioactivity of the natural radioelements but was of a new type, since the electrons emitted were positive. The formation of atoms emitting delayed positive electrons appeared to be associated with the emission of neutrons, which had been previously observed, according to the nuclear reaction

These atoms therefore had to be atoms of a radioactive isotope of phosphorus that would be transformed by the emission of positive electrons and neutrinos into atoms of one of the known stable isotopes of silicon:

The similar production, by the irradiation of boron with α rays, of a radioelement emitting positive electrons possessing a period of more than ten minutes was also established; this radioelement had to be an isotope of nitrogen. Frédéric Joliot and Irène Curie announced their discovery of a new type of radioactivity and of the artificial formation of light radioelements in a note to the Academy of Sciences on 15 January 1934. Within less than two weeks after their announcement they were able to conceive and skillfully execute radiochemical experiments proving that the radioelement formed in aluminum bombarded with α rays had exactly the same chemical properties as phosphorus and that the one formed in boron had those of nitrogen.

These elegant experiments, which provided the first chemical proof of induced transmutations and showed the possibility of artificially creating radioisotopes of known stable elements, were repeated and extended in the major nuclear physics laboratories of various countries. In Italy, Enrico Fermi demonstrated that neutron bombardment of most elements, even those of high atomic mass, gave rise to radioelements emitting negative electrons, often isotopes of the initial element. The next year, in November 1935, Frédéric Joliot and Irène Curie were awarded the Nobel Prize in chemistry for “their synthesis of new radioactive elements.”

Thirty-five years old and at the height of his scientific career, Joliot had fully developed his personality. Slightly taller than average, with black hair and black eyes, a lively expression, and an athletic appearance, he possessed considerable charm. He was a brilliant conversationalist who loved to please and to be admired. An avid and exceptionally good skier, sailor, and tennis player, he was also an enthusiastic and skillful hunter and fisherman. Joliot had a taste for certain luxuries that wealth brought but was deeply attracted to the common people; he enjoyed spending time with workers and sailors, with whom he was able to communicate easily. Politically a socialist, he was active in antifascist organizations.

The fame that came with the Nobel Prize brought Joliot numerous responsibilities that interrupted his research for several years. Named professor at the College de France in 1937, he sought to equip its new laboratories with the instruments needed for the study of nuclear reactions; he directed the construction of a 7 MeV cyclotron and a 2,000,000-volt electric pulse accelerator.

At the beginning of 1939 the great Germab radiochemist Otto Hahn published chemical data proving that the nucleus of a uranium atom can be split into two nuclei of similar mass by the impact of a neutron. Within a few days Joliot furnished a direct physical proof of the explosive character of this bipartition of the uranium atom, subsequently called fission. In an elegantly simple experiment he demonstrated that the radioactive atoms produced in a thin layer of uranium by a flux of neutrons are ejected with a velocity sufficient to permit them to pass through a thin sheet of cellophane. The great kinetic energy of the fission fragments was established independently by this experiment and by the one done in Copenhagen by O. R. Frisch, who employed a proportional pulse amplifier. Pursuing the study of this phenomenon, Joliot was incontestably the first, in collaboration with Hans von Halban and Lew Kowarski, to prove that the fission of uranium atoms is accompanied or followed by an emission of neutrons (uranium submitted to a flux of slow neutrons emits rapid neutrons) and subsequently that the fission of a uranium atom induced by one neutron produces, on the average, an emission of several neutrons (March- April 1939). It was now possible to envision, as Joliot immediately did, a process in which uranium atoms would undergo successive fissions linked in divergent chains by neutrons and consequently developing like an avalanche. Hence an immense number of atoms, constituting a ponderable mass of uranium, might be disintegrated within a relatively short time by the minute excitation due to a single neutron.

The principle of the liberation of the internal energy of uranium atoms had thus been discovered, and the conditions in which the nuclear chain reactions could develop were rapidly determined. In particular it became apparent that it would be necessary to slow down the neutrons emitted during fission by joining to the uranium a “moderator” containing light atoms absorbent of neutrons and that the best moderator would be heavy water. For this reason Joliot, who had obtained about six tons of uranium oxide from the Belgian Congo, ordered form Norway the only sizable stock of heavy water then existing. The heavy water arrived safely in Paris even though World War II had begun, but there was too little time before the invasion of France for it to be used there. Joliot decided to remain in France but had Halban and Kowarski carry the precious substance with them to England to continue the group’s investigations. In Paris, Joliot discontinued all his work on atomic energy that might benefit Germany. While continuing research in pure physics, he became increasingly involved in dangerous resistance activities, working closely with millitant Communists; in 1942 he joined the then clandestine Communist party.

Following the liberation of France and the explosion of the first atomic bombs, Joliot, foreseeing the potential industrial importance of atomic energy and convinced of the impossibility of obtaining sufficient money for any fundamental research in nuclear physics not linked with practical applications, persuaded General de Gaulle, president of the provisional government, to create an atomic energy commission. Established in October 1945, this commission was endowed with broad powers and substantial funds. The new organization was headed by Joliot, who as high commissioner was responsible for scientific and technical activities, and by a chief administrator responsible for administrative and financial matters. Joliot assembled a dynamic group, and under his vigorous direction France’s first atomic pile began operation in December 1948; in the same year a valuable uranium deposit had been discovered near Limoges. The first laboratories, which were installed in a former fort, became inadequate. Joliot persuaded the government to build a major nuclear research center on the plateau of Saclay, twelve miles south of Paris, and he supervised the construction of its first equipment.

Under pressure from the Communist party Joliot publicly took positions irritating to the government, although they were not of the sort to cast doubt on the loyalty with which he performed his duties. Using as a pretext a declaration of Joliot’s in which he stated that he would never participate, in his capacity as a scientist, in a war against the Soviet Union, the president of the Council, Georges Bidault, removed him form his functions as high commissioner in April 1950. Although he had partially provoked it, Joliot suffered from this dismissal. Since the war, in fact, he had often seemed a tormented spirit, plagued by deep self-doubt despite his brilliant successes and seeking in the adulation of crowds compensation for the reserve that he sometimes perceived among his peers.

After 1950 Joliot once again gave most of his time to his laboratory and to his teaching at the College de France, but he felt he should dedicate his best efforts to what seemed to him the most effective struggle against the threat of war; he lent his great prestige to the World Organization of the Partisans of Peace, whose president he had become. He was greatly shaken by the death of his wife in March 1956, at a time when he had just survived a very serious attack of viral hepatitis. He succeeded Irène Joliot- Curie as head of the Radium Institute, where, with her, he had done his finest work. He carried out these new duties with devotion and enthusiastically supervised the relocation of the Institute in its new laboratories, then under construction in Orsay. His health remained delicate; he died on 14 August 1958, at the age of fifty-eight, following an operation made necessary by an internal hemorrhage. General de Gaulle, who had again become head of the government, decided that Joliot, whom thirteen years earlier he had appointed High Commissioner for Atomic Energy, should receive a state funeral.

BIBLIOGRAPHY

I. Original Works. The works of Frédéric and Irène Joliot-Curie are collected in Oeuvres scientifiques complètes (Paris, 1961). A selection of his work is in Textes choisis (Paris, 1959). His principal scientific publications include “Sur une nouvelle méthode d’étude du dépôt électrolytique des radio-éléments,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 184 (1927), 1325; (with Irène Curie) “Sur le nombre d’ions produits par les rayons alpha du RaC′ dans l’air,” ibid., 186 (1928), 1722; 187 (1928), 43; (with Irène Curie) “Sur la nature du rayonnement absorbable qui accompagne les rayons alpha du polonium,” ibid., 189 (1929), 1270; “étude électrochimique des radioéléments,” in Journal de chimie physique, 27 (1930), 119; (with Irène Curie) “Rayonnements associés à l’émission des rayons alpha du polonium,” in Comptes rendus , 190 (1930), 27; “Sur la détermination de la période du Radium C′ par la méthode de Jacobsen. Expérience avec le thorium C′,” ibid., 191 (1930), 1292; (with Irène Curie) “Étude du rayonnement absorbable accompagnant les rayons alpha du polonium,” in Journal de physique et le radium, 2 (1931), 20.

For further reference, see “Sur la projection cathodique des éléments et quelques applications” and “Propriétés électriques des métaux en couches minces préparées par projection thermique et cathodique,” in Annales de physique, 15 (1931), 418; “Le phénomène de recul et la conservation de la quantité de mouvement,” in Comptes rendus hebdomadaires des séances de l’Académie des sciences, 192 (1931), 1105; (with Irène Curie) “Préparation des sources de polonium de grande densité d’activité,” in Journal de chimie physique, 28 (1931), 201; “Sur l’excitation des rayons gamma nucléaires du bore par les particules alpha. Energie quantique du rayonnement gamma du polonium,” in Comptes rendus . . . des sciences, 193 (1931), 1415; (with Irène Curie) “Émission de protons de grande vitesse par les substances hydrogénées sous l’influence des rayons gamma très pénétrants,” ibid., 194 (1932), 273; (with Irène Curie) “Effect d’absorption de rayons gamma de très haute fréquence par projection de noyaux légers,” ibid., 194 (1932), 708; (with Irène Curie) “Projection d’atomes par les rayons très pénétrants excités dans les noyaux légers,” ibid., 194 (1932), 876; (with Irène Curie) “Sur la nature du rayonnement pénétrant excité dans les noyaux légers par les particules alpha,” ibid., 194 (1932), 1229; (with Irène Curie and P. Savel) “Quelques expériences sur les rayonnements excités parl les rayons alpha dans les corps légers,” ibid., 194 (1932), 2208; (with Irène Curie) “New Evidence for the Neutron,” in Nature, 130 (1932), 57; (with Irène Curie) “L’existence du neutron,” in Actualités scientifiques et industrielles (Paris, 1932); (with Irène Curie) “Sur les conditions d’émission des neutrons par actions des particules α sur les éléments légers,” in Comptes rendus . . . des sciences, 196 (1933), 1106; (with Irène Curie) “Contribution à l’étude des Électrons positifs,” ibid., 196 (1933), 1105; and (with Irène Curie) “Sur l’origine des électrons positifs,” ibid., 196 (1933), 1581.

Other of Joliot’s papers are: (with Irène Curie) “Preuves expérimentales de l’existence du neutron,” in Journal de physique et la radium, 4 (1933), 21; (with Irène Curie) “électrons positifs de transmutation,” in Comptes rendus . . . des sciences, 196 (1933), 1885; (with Irène Curie) “Nouvelles recherches sur l’émission des neutrons,” ibid., 197 (1933), 278; (with Irène Curie) “Lacomplexité du proton et la masse du neutron,” ibid., 197 (1933), 237;(with Irène Curie) “Mass of the Neutron,” in Nature, 133 (1934), 721; (with Irène Curie) “électrons de matérialisation et de transmutation,” in Journal de physique, 4 (1933), 494; (with Irène Curie) “Rayonnement pénétrant des atomes,” 7ème Conseil de physique Solvay, 22 ocotobre 1933 (Paris, 1934), p. 121; “Preuve expérimentale de l’annihilation des électrons positifs,” in Comptes rendus . . . des sciences, 197 (1933), 1622; “Sur la dématérialisation de paires d’électrons,” ibid., 198 (1934), 81; “Preuve expéimentale de l’annihilation des électrons positifs,” in Journal de physique, 5 (1934), 299; “Le neutron et le positron,” in Helvetica acta, 81 (1934), 211; (with Irène Curie) “Un nouveau type de radioactivé,” in Comptes rendus . . . des sciences, 198 (1934), 254; (with Irène Curie) “Artificially Produced Radioelements,” Joint Conference of the International Union of Pure and Applied Physics, and the Physical Society, 1 (Cambridge, 1934); (with Irène Curie) “Production artificielle d’éléments radioactifs” and “Preuve chimique de la transmutation des éléments,” in Journal de physique, 5 (1934), 153; “Realisation d’un appareil Wilson pour pressions variables (1 cm de Hg à plusieurs atmosphères),” in Journal de physique, 5 (1934), 216; étude des rayons de recul radioactifs par la méthode des détendes de Wilson,” ibid., 5 (1934), 219; (with Iréene Curie and P. Preiswerk) “Radioéléments créés par bombardment de neutrons. Nouveau type de radioactivé,” in Comptes rendus . . . des sciences, 198 (1934), 2089.

Other works include “Les nouveaux radioéléments. Preuves chimiques des transmutations,” in Journal de chimie physique, 31 (1934), 611; (with Irène Curie) “L’électron positif,” in Actualités scientifiques et industrielles (Paris, 1934); (with L. Kowarski) “Sur la production d’un rayonnement d’énergie comparable à celle des rayons cosmiques mous,” in Comptes rendus . . . des sciences, 200 (1935), 824; (with A. Lazard and P. Savel) “Synthèse de radioéléments par des deutérons accélérés au moyen d’un générateur d’impulsions,’ ibid., 201 (1935), 826; (with Iréne curie) “Radioactivité artificielle,” in Actualités scientifiques et industrielles (Paris, 1935);(with I. Zlotowski) “Sur l’énergie des groupes de protons émis lors de la transmutation du bore par les rayons a,” in comptes rendus, 206 (1938), 750; (with I. Zlotowski) “Formation d’un isotope stable de masse 5 de l’hélium lors collisions entre hélions et deutérons,’ in Journal de physique, 9 (1938), 403; (with I. Zlotowski) “Sur la détermination par la méthode Wilson de la nature et l’énergie des particules émises lors des transmutations. Application aá la réaction ,” ibid., 9 (1938), 393; “Preuve expérimentale de la rupture explosive des noyaux d’uranium et de thorium sous l’action des neutrons,” in Comptes rendus . . . des sciences,208 (1939), 341; “Observations par la méthode Wilson des trajectoires de brouillard des produits de l’explosion des noyaux d’uranium,” ibid., 208 (1939), 647; “Sur la rupture explosive des noyaux U and Th sous l’action des neutrons,” in Journal de physique, 10 (1939), 159; (with L. Dodé. H. von Halban, L. Kowarski) “Sur l’é des neutrons libérés lors de la partition nucléaire de l’uranium,” in Comptes rendus . . . des science, 208 (1939), 995; and (with H. von Halban and L. Kowarski) “Liberation of Neutrons in the Nuclear Explosion of Uranium,” in Nature, 143 (1939), 470.

See also: (with H. von Halban and L. Kowarski) “Number of Neutrons Liberated in the Nuclear Fission of Uranium,” in Nature,143 (1939), 680;(with H. von Halban and L. Kowarski)“Energy of Neutrons Liberated in the Nuclear Fission of Uranium Induced by Thermal Neutrons” ibid., 143 (1939), 939; (with H. von Halban, L. Kowarski, and F. Perrin) “Mise en évidence d’une réaction nucléaire en chaine au sein d’une masse uranifère,” in Journal de physique, 10 (1939), 428; (with B. Lacassagne) “Cancer du foie apparu chez un lapin irradié par les neutrons,” in Comptes rendus . . . des science, 138 (1944). 50;“Sur une méthode de mesure de parcours des radioéléments de nature chimique déterminée, projectés lors de la bipartition de l’uranium,” ibid., 218 (1944), 488; (with Iréne Curie) “Sur la bipartition de l’ionium sous l’action des neutrons,” in Annales de physique19 (1944), 107; “Sur une méthode physique d’extraction des radioéléments de bipartition des atomes lourds et mise en évidence d’un radiopraséodyme de période 13 j,” in Comptes rendus . . . des sciences, 218 (1944), 733; (with R. Courrier, A. Horeau, and P. Süe) “Sur l’obtention de la thyroxine marquée le radioiode et son comportement dans l’organisme,” ibid ., 218 (1944), 769; (with H. von Halban and L. Kowarski) “Sur la possibilité de produire dans un milieu uranifére des réactions nucléaires en chaine illimitée. 30 octobre 1939,” ibid., 299 (1949), 19; and (with Iré Curie)“Sur l’étalonnage des sources de radioéléments,” “Commission Mixte des Unions Internationales” de Physique et de Chimie, Juillet 1953.

II. Secondary Literature. Louis de Broglie, La vie et l’oeuvre de Frédéric Joliot (Paris, 1959); P. M. S. Blackett, “Jean-Frédéric Joliot”, in Biographical Memoirs of Fellows of the Royal Society, 6 (Nov. 1960), and Pierre Biquard, Fédéric Joliot-Curie (Paris, 1961).

Francis Perrin

Jean Frédéric Joliot-Curie

The French physicist Jean Frédéric Joliot-Curie (1900-1958) discovered artificial radioactivity and the emission of neutrons in nuclear fission.

Frédéric Joliot was born in Paris on March 19, 1900, the youngest of six children whose father had served in the militia of the Paris Commune 30 years earlier. While a student of Paul Langevin at the School of Physics and Chemistry in Paris, he received in 1925 an assistantship at the laboratory of the Radium Institute of Marie Curie, the discoverer of radioactivity. There he met and the next year married Irène Curie, the elder daughter of Madame Curie, who pursued her research at her mother's laboratory, and added his wife's surname to his own.

The union of Irène and Frédéric constituted in the history of science an outstanding example of husband-wife teamwork. Among the 26 papers published jointly by the Joliot-Curies during the first 10 years of their partnership was the 1932 paper announcing a penetrating radiation from beryllium when bombarded with alpha rays. In a 1934 paper they disclosed their greatest discovery, the artificial production of radioactive elements. They achieved this by bombarding certain light elements, such as aluminum, boron, and magnesium, with alpha radiation. The significance of this discovery was that it allowed scientists to study more systematically the patterns of nuclear transformations. For this achievement they received the Nobel Prize in chemistry in 1935.

Two years later Joliot-Curie, as newly appointed professor at the Collège de France, launched the development of a research center in nuclear physics. He and his collaborators established for the first time that approximately three fast neutrons were produced when a uranium atom was fissioned by slow neutrons. From this they concluded shortly afterward that a chain reaction in uranium was a distinct possibility.

After World War II Joliot-Curie's scientific activity largely concerned the reorganization of French atomic and nuclear research. At his recommendation the French government set up the Commissariat à l'Énergie Atomique, on which Joliot-Curie served as high commissioner. He had to resign from this post in 1950 because of his most vocal advocacy of the aims and policies of the French Communist party, of which he had been a member since 1942. His last 8 years were spent in directing research at the Centre National de la Recherche Scientifique and at the Collège de France, where during his tenure he offered 13 different courses in advanced physics. Upon the death of his wife in 1956, Joliot-Curie succeeded her as the director of the Curie Laboratory of the Radium Institute. His last contribution to the cause of French science, a new and large nuclear research center at Orsay, had just become operational when he died in Paris on Aug. 14, 1958.

Further Reading

The most accessible though highly partisan account of Joliot-Curie's life and work in English is Pierre Biquard, Frédéric Joliot-Curie (trans. 1965). Shorter, but scientifically informative, is the biographical essay by P. M. S. Blackett in Biographical Memoirs of Fellows of the Royal Society, vol. 6 (1960). □