BECQUEREL, JEAN ANTOINE EDMOND MARIE

(b. Paris, France. 5 February 1978; d, Sainte-Marguerite, near Pornichet, Brittany, France. 4 July 1953)

physics.

Jean was the fourth Becquerel to hold the chair of physics at the Museum of Natural History in Paris. He was raised in the house at the Jardin des Plantes that had been the home, in turn, of his greatgrandfather, Antoine-César Becquerel (1788–1878); his grandfather, Edmond (1820–1891); and his father, Henri (1852–1908). His mother, Lucie Jamin, was the daughter of J. C. Jamin, professor of physics at the Sorbonne. The distinguished line of physicists ended with Jean Becquerel, who married in 1921 but had no children.

It is hardly surprising that Becquerel’s first toys included magnets and electroscopes or that he entered the École Polytechnique (1897) after graduating from the Lycée Louis-le-Grand. In 1903, the year that Henri Becquerel shared the Nobel Prize for physics with Marie and Pierre Curie, Jean Becquerel completed his education at the École des Pouts et Chaussées and became an assistant in physics at the Museum of Natural History, where he succeeded his father in 1909. During World War I. Becquerel directed construction of fortifications and trenches and carried out research on optical signals at sea. After the war he commuted to Paris from Fontainebleau, continuing to work in the physics laboratory established in 1938 in the house where Georges Cuvier had lived.

In addition to his research m physics, Becquerel became known for his lectures not only at the Museum of Natural History but also at the École Polytechnique, where he uas tutor, examiner, and. from 1919 to 1922, temporary professor. With Paul Langevin. Becquerel was one of the few Fiench physicists teaching quantum theory and Einstein’s relativity theory in the 1920s, In addition, Becquerel was innovative in his teaching of thermodynamics by employing the new physics of atomism and kinetic theory. Had he lectured regularly at the École Polyteehnique, the Sorbonne, or the Collège de France rather than at the Museum of Natural History, his teaching might have exerted greater influence on the new physics in France.

Becquerel’s principal researches were in spectroscopy and magneto-optics, areas of traditional strength in French science, for these researches he received the Hughes Prize (1913) and the La Caze Prize (1936), and he was elected to the Academy of Sciences (1946). He continued his father’s 1888 doctoral researches on the variations of the absorption spectra in crystals and on magnetic rotatory polarization, as well as his family’s long-standing interest in phosphorescence. In 1908 hecoauthored a paper with his father on the photoluminesccnce of uranyl salts at low temperatures.

Becquerel’s fundamental line of research began in 1906 with an attempt to study the effect of a magnetic field on the optical properties of crystals. Building upon knowledge of the Zeeman effect for gases and vapors, Becquerel found a superficially similar effect in rare-earth crystals having a very fine spectrum of absorption bands. Analyzing doublets produced in a magnetic field, Becquerel argued for the existence of both positive and negative electrons. Although his interpretation proved erroneous, he later cited the discovery of the positron as a views.

Influenced by Pierre Curie’s experimental work and Paul Langevin’s classical electron theory relating magnetic susceptibility to temperature, Becquerel reasoned that the purely magnetic properties of rareearth crystals could be more easily identified at very low temperatures, when intramolecular thermal motions decline. Placing crystalline films or solutions inside a vacuum tube containing liquid air, Becquerel found that some absorption bands weakened or disappeared, while others became better defined and more intense than at ordinary temperatures. His work caught the attention of Heike Kamerlingh Onnes, whose laboratory at Leiden was assuming leadership in low-temperature physics. Collaboration between Becquerel and Kamerlingh Onnes began in early 1908 and continued with other Dutch physicists; Becquerel moved his spectrograph to Leiden and spent one or two months there each year. He thus became a regular contributor to the most influential and largely English-language journal of lowtemperature physics, Communications from the Physical Laboratory at the University of Leiden.

At Leiden, Becquerel studied spectra at the temperatures of liquid hydrogen and liquid helium, describing what he called the’ fundamental spectrum’ of rare-earth crystals, rubies, emeralds, and other substances in the range of 4.2°–1.3°K. In the period 1925–1930 he studied paramagnetic rotatory polarization, explaining these effects by the hypothesis of an internal electric field and interesting himself in a quantum interpretation. Becquerel’s collaboration with Wander J. de Haas and Hendrik A. Kramers in the late 1920’s and early 1930’s was especially useful for determining properties associated with electron spin. Investigations of ironcontaining crystals that exhibit magnetic rotation at very low temperatures in a magnetic field revealed properties of hysteresis that Becquerel christened “metamagnetism,”

Becquerel’s earliest published researches occasioned some notoriety because of their support for the existence and properties of “N rays,” a spurious discovery made by René Blondlot in 1903. Becquerel and André Broca, professor of medicine at the University of Paris, investigated the effects of anesthetics in suppressing the supposed emission of N rays from living bodies. He also studied the deviability of N rays in a magnetic field, looking for the kinds of effects associated with the uranium rays discovered by his father. Becquerel later attributed his mistakes in these investigations to inexperience and to self-delusion resulting fiom the influence of older physicists who were family friends.

BIBLIOGRAPHY

I. Original Works. Among Becquerel’s writings are “Absorption de la lumière et phénomènes magnéto-optiques dans les composés de terres rares aux très basses températures,” in Het natuurkundig laboratirium der Rijksuniversiteit te Leiden in de jaren 1904–1922 (Leiden, 1922), 228–361: Le principle de relativité et la théorie de la gravitation (Paris, 1922): Cours de physique à l’usage des élèves de l’enseignement supérienr et desingénieurs, 2 vols. (Paris. 1924–1926): and Notice sur les travaux scientifitques de Jean Becquerel, 2 vols. (Paris. 1934).

II. Secondary Literature. Louis de Broglie. “Notice sur la vie et l’oeuvre de Jean Becquerel.” in Instittu de France. Acadénue des Sciences. Notices et discours, 5 (1963–1972), 1–20, has a portrait: Yves Le Grand. “Jean Becquerel (1878–1953),” in Archives du Muséum national d’histoire naturelle, 7th ser. 3 (1954–1955). v-wviii, includes a portrait and a bibliography.

Mary Jo Nye