Dunoyer De Segonzac, Louis Dominique Joseph Armand

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Dunoyer De Segonzac, Louis Dominique Joseph Armand

(b. Versailles, France, 14 November 1880; d. Versailles, 27 August 1963)


Dunoyer was the son of Anatole Dunoyer, a founder of the École des Sciences Politiques in Paris, and Jeanine Roquet. He married Jeanne Picard, daughter of Émile Picard, on 4 June 1907. They had two sons, whose studies Dunoyer supervised himself.

As a youth, Dunoyer placed first in the general physics competition and was second on the admissions list of the Éole Polytechnique and first on that of the Éole Normale Supérieure. He chose to attend the latter (1902–1905), which oriented him toward teaching and research. He placed first in the physics agrégation in 1905 and in that year was an assistant to P. Langevin at the Collège de France. His first research concerned the difficulties of compensating compasses in iron and iron-clad ships. This work furnished the subject for his doctoral thesis1 and took concrete form in the dygograph and the type of electromagnetic compass2 that was mounted i n Lindbergh’s Spirit of St. Louis. In 1908 he won the Prix Extraordinaire de la Marine3 for his research in magnetism.

A Carnegie scholar in the laboratory of Marie Curie in 1909, Dunoyer conducted the fundamental experiment on molecular beams in 1912.4 Originally designed to verify the kinetic theory, the experiment also resulted in the preparation of thin films of alkali metals. “He showed that in a good vacuum one could obtain a linear beam of molecules, but that if the vacuum degenerated, the impacts of the molecules against each other produced a broadening and a disintegration of the beam.”5 (This work was followed by the studies of the properties of molecules, without perturbation, by Otto Stern and others.) This experimental demonstration of the kinetic theory of gases was the origin of the preparation of thin films by thermal vaporization and of the studies of the properties of atoms and molecules by the so-called molecular ray method.6 In 1912 Dunoyer was awarded the Subvention Bonaparte7 for his work on the fluorescence of pure sodium vapor and for the complete investigation of the fluorescence and absorption spectra of the alkaline metals. In 1913 he won the Prix Becquerel for his research on the electrical and optical properties of metallic vapors, notably of sodium vapor.8 In the same year he was appointed deputy professor at the Conservatoire National des Arts et Métiers. He studied the surface resonance of sodium vapor with R. W. Wood in 1914.

An aviation officer and inspector, Dunoyer was wounded and became chevalier of the Legion of Honor, receiving the Croix de Guerre in 1915 as well. He became interested in meteorology and aerial navigation and invented a bombsight.9 In 1918 he was awarded the Prix Danton for his work on radiant phenomena.10

Dunoyer became a lecturer at the Institut d’Optique in 1919. He was physicist at the observatory of Meudon from 1927 to 1929 and professor at the Institut d’Optique from 1921 to 1941. He participated in the founding of the Société de Recherches et de Perfectionnements Industriels, and while secretary-general of the Société Française de Physique he devised a special lens for the illumination of atomic beams. A glassblower and remarkable technician, he improved the procedures of Wolfgang Gaede (1913) and of Langmuir (1916) and developed various diffusion pumps and devices for measuring very low temperatures. These accomplishments brought him the Subvention Loutreuil in 1925.11

Simultaneously Dunoyer pursued his research on photoelectricity and the construction of photoelectric cells; the first application (1925) was to talking movies, where a potassium cell was employed. He won the Prix Valz in 1929 for his research on the spirit level and on photoelectric cells.12 In 1930 he was awarded the Subvention Loutreuil for the continuation of his research on photoelectric cells.13

In 1935 Dunoyer’s studies on thermal vaporization in a vacuum enabled him to construct the first aluminized mirrors.14 On 10 February 1937 he was elected artist member of the Bureau des Longitudes, replacing Louis Jolly. From 1941 to 1945 he was titular professor at the Sorbonne and director of the Institut de Chimie Physique, where he taught a remarkable course on the kinetic theory of gases. Dunoyer was named honorary president of the Société des Ingénieurs du Vide, in whose journal, Le vide, he published seven articles between 1949 and 1956. The society dubbed him “Grandfather of the Vacuum.”


1. The thesis was under the direction of E. E. N. Mascart and P. Langevin and was entitled Étude sur les compas de marine et leurs méthodes de compensation. Un nouveau compas électromagnétique (Paris, 1909). It is thèse Fac. Sciences Paris, no. 1336.

2. See Comptes rendus hebdomadaires des séances de l’Académie des sciences, 145 (1907), 1142–1147, 1323–1325; 147 (1908), 834–837, 1275–1277; Bulletin de la Société française de physique, 295 (1909–1910); Revue maritime, 315 (1910). The Comptes rendus are hereafter cited as CR.

3. See CR, 147 (1908), 1111, 1113–1117, for his electromagnetic compass tested on the battleship Patrie and the dygograph placed on the battleship Danton. It replaced the ordinary compass, which was rendered useless by rarefaction of the magnetism, resulting from the ship’s armor.

4. See CR, 152 (1911), 592–595; 153 (1911). 333–336; 154 (1912), 815–818, 1344–1346; 155 (1912), 144–147, 270–273; 157 (1913), 1068–1070; 158 (1914), 1068–1071, 1265–1267, written with R. W. Wood; Bulletin de la Société française de physique, four memoirs between 1912 and 1914; Journal de physique et radium, 185 (1913); Collection de mémoirs relatifs à la physique (1912); Radium, seven memoirs between 1910 and 1914.

5. Robert Champetx, Le vide (Paris, 1965).

6.Le vide, 106 (July-Aug. 1963).

7. See CR, 155 (1912), 93, 1407.

8. See CR, 157 (1913), 1287.

9. See CR, 165 (1917), 1068–1071, written with G. Reboul; 166 (1918), 293–295; 168 (1919), 47, 138, 457–459 (with Reboul), 785–787 (with Reboul), 726–729, 1102–1105; 169 (1919). 762, 78–79, 191–193 (the last two written with Reboul); 170 (1920), 744–747 (with Reboul); 173 (1921), 1101–1104; Bulletin de la Société française de physique (1920); Technique aéronautique (1921).

10. See CR, 167 (1918), 829.

11. See CR, 181 (1925), 1012, 1016. At the same time he was given money from the research fund of the secretary-general of the Société Française de Physique in order to pursue his investigations of certain problems concerning modern methods of measuring high vacuums.

12. See CR, 189 (1929), 1123.

13. See CR, 191 (1930), 1245. See also CR, 174 (1922), 1615–1617 (written with P. Toulon); 176 (1923), 953–955, 1213; 179 (1924), 148–151, 461–464, 522–575 (all written with P. Toulon); 182 (1926), 686–688; 185 (1927), 271–273; 196 (1933), 684–686 (written with Paounoff); 198 (1934), 909–911; 200 (1935), 1835–1838; Bulletin de la Société française de physique, 13 memoirs between 1922 and 1930; Revue d’optique théorique et instrumentale, 11 memoirs between 1922 and 1948; Journal de physique et radium, 2 memoirs.

14. See CR, 202 (1936), 474–476; 220 (1945), 520–522, 686–688, 816–817, 907–909; 221 (1945), 97–99; 230 (1950), 57–58; 232 (1951), 1080–1082; 233 (1951), 125, 919–921.


In addition to the articles cited in the notes, see La technique du vide (Paris, 1924); Les émissions électroniques des couches minces (Paris, 1932); Les radiations monochromatiques (Paris, 1935); “Les cellules photoeléctriques,” in Comptes rendus. 2° Congrès international d’électricité (Paris, 1936); Allocution pour le vingtième anniversaire de la mécanique ondulatoire (Paris, 1944); Le vide et ses applications, in the series Que Sais-je?, no. 430 (Paris, 1950).

His articles published in Le vide are “Étude d’un micromanomètre thermique, précédée de quelques remarques générales sur ce type d’instrament,” 4 (1949), 571–581, 603–618, 643–660; “Sur certaines phénomènes de dédegagement gazeux observés pendant le pompage de lampes à incandescence à basse tension,” 5 (1950), 793–806; “Quelques remarques sur les formules de l’écoulement des gaz raréfiés dans les canalisations,” ibid, 881–886; “Bases théoriques de la dessication dans le vide,” 6 (1951), 1025– 1040, 2077–2090; “Expériences sur l’évaporation de l’eau dans le vide et comparaison avec la théorie,” 8 (1953), 1280–1294; “Fonctionnement des condensateurs de vapeur d’eau dans les appareils de dessication dans le vide,” 10 (1955), 165–184; and “Quelques appareils pour la production de faisceaux moléculaires et quelques expériences sur ceux de sodium en resonance optique,” 11 (1956), 172–189.

P. Berthon