Louis Dunoyer de Segonzac

Louis Dominique Joseph Armand Dunoyer de Segonzac (born November 14, 1880 in Versailles ; † August 27, 1963 there ) was a French physicist.

Dunoyer came from an influential family, was first in the general examinations for admission to the elite universities in France in physics and first in the overall result in those for the École normal supérieure (Paris) (ENS) and second in those for the École Polytechnique and started 1902 studies at the ENS. In 1905 he was first with Paul Pascal in the agrégation exams in physics and entered Paul Langevin's laboratory at the Collège de France . He received his doctorate in 1909 under Langevin and Eleuthère Mascart (with a dissertation in which he developed an electromagnetic compass, the first of its kind, which was used by Charles Lindbergh when he crossed the Atlantic, among others ), was then on a Carnegie grant in the laboratory of Marie Curie and in 1913 became professor at the Conservatoire national des arts et métiers. In 1914 he was drafted at the beginning of the First World War, served with the aviators and as an inspector, was wounded, received the Croix de guerre and became a Knight of the Legion of Honor and was dismissed as a first lieutenant in the reserve. From 1920 he taught at the École supérieure d'optique, became Maître de conférences in 1922 and professor (without a chair) in applied optics at the Sorbonne in 1927. He was also a physicist at the Meudon Observatory from 1927 to 1929. In 1937 he was elected to the Bureau des Longitudes . In 1941 he was President of the French Physical Society. In the same year he was given the chair of Jean Perrin , who was in exile in the USA, in a controversial manner . In 1945 he was replaced on the chair by Edmond Bauer .

Dunoyer was considered an excellent and technically skilled experimental physicist (he was also a good glassblower, for example).

In 1911 he invented the molecular or atomic beam method. He showed that with a small window in a furnace with an atomic or molecular gas, you could get an atomic or molecular beam. That made him known internationally. His method was used by the American Robert W. Wood for spectroscopic investigations (who also worked with Dunoyer in 1914 on resonance radiation from sodium vapors) and expanded by Otto Stern in 1919 and applied spectacularly in the Stern-Gerlach experiment .

In 1913 he received the Prix ​​Becquerel for his work on electrical and optical properties of metal vapors, especially those of sodium. He dealt with the photoelectric effect (and constructed photocells, which he also used in experiments on sound film in 1925), improved methods of vacuum technology by Wolfgang Gaede and Irving Langmuir and developed methods for measuring low temperatures. His experiments with metal vapors in a vacuum made it possible to manufacture mirrors with an aluminum coating for the first time. He received the Prix ​​Valz in 1929 for developing photocells and spirit levels .

Politically, he was on the right. In 1935 he signed a manifesto in support of the invasion of fascist Italy in Ethiopia (Manifeste des intellectuels français pour la défense de l'Occident et la paix en Europe). He was a member of the Cercle Fustel de Coulanges , which was an offshoot of Action française , was a supporter of Charles Maurras and was also close to the royalists.

In 1906 he married the daughter Jeanne (1882-1970) of the mathematician Émile Picard , with whom he had two children. Èmile Picard had also been one of his teachers (Dunoyer's first publication in 1906 was in mathematics).

Fonts

• Etudes sur les compas de marine et leurs méthodes de compensation: Un nouveau compas électromagnétique, Gauthier-Villars 1909 (= dissertation)
• Vacuum practice, Bell and Sons 1926 (French original La technique de vide, Paris: Blanchard 1924)
• Le vide et ses applications, Presses Universitaires de France 1950

Web links

• Entry by Michel Barran about him at Science World, Eric Weisstein
• Idref
• Genealogical website (Geneanet)