Aimé Cotton
Aimé Auguste Cotton ( born October 9, 1869 in Bourg -en- Bresse, † April 16, 1951 in Sèvres ) was a French physicist who is known for the study of the interaction of light with chiral molecules. In the absorption bands of these molecules, he discovered large values of optical rotatory dispersion (ORD ), or the variation of the optical rotation as a function of wavelength (Cotton -Mouton effect), as well as circular birefringence or differences in absorption between right - and left-circularly polarized light ( circular dichroism ).
Life and work
Aimé Cotton was born on October 9, 1869 in Bourg -en- Bresse, Ain. His grandfather was a director of the École normale ( Teachers College ) of Bourg, and his father, Eugene Cotton, was a professor of mathematics at the University of Bourg, where the physicist André- Marie Ampère began his career. His brother Émile Cotton was a mathematician and academician.
Aimé Cotton attended a Lycée in Bourg -en- Bresse and then the mathematical special program at the Lycée " Blaise Pascal " in Clermont -Ferrand. He entered the École Normale Supérieure in 1889, and won the final in 1893 the physical science prize.
As a graded student at the Physics Laboratory of the Ecole normale supérieure, he prepared then before his PhD in physics. In this work he studied the relationships of polarized light by optically active substances, which contain chiral molecules. In (absorption spectroscopy) absorption band of these substances, it was large variations of optical rotation as a function of wavelength, which are useful as optical rotatory dispersion (ORD ), or as the Cotton effect is known today. He also discovered the related phenomenon of circular dichroism, the unequal absorption of right - and left-circularly polarized light in a material. These two phenomena were later used to determine the stereochemistry of chiral molecules in organic chemistry and biochemistry.
He was appointed Maître de conférences in the science faculty in Toulouse in 1895 and defended his PhD thesis in 1896 before the faculty of the University of Paris. His dissertation was titled research on the absorption and dispersion of light by substances which are capable of optical rotation (French Recherches sur l' absorption et la lumière par les de la dispersion milieux DOUES du pouvoir rotatoire ). In 1900 he was appointed as a temporary replacement for Jules Violle for faculty ( associate professor, lecturer ). In 1904 he became an instructor and in 1910 professor at the Science Faculty of the University of Paris, from where he was assigned to the École Normale Supérieure, and remained until 1922.
During this time, he conducted research in the field of interaction of light and magnetism. He first worked with Pierre -Ernest Weiss on the Zeeman effect, the splitting of spectral lines in the presence of a magnetic field. For this work he invented a cotton- scale to measure the intensity of the magnetic field accurately. (Another Cotton - scale has been previously invented by William Cotton. ) With White, he studied the magnetic splitting of the blue lines of the zinc atom and in 1907 they were able, the ratio between the electron charge to its mass ( e / m) with greater precision to measure than with the method of Joseph John Thomson.
Cotton then became interested in the Faraday effect in the vicinity of absorption lines and showed the magnetic circular dichroism. At the same time he worked with his former classmate Henri Mouton, a biologist at the Pasteur Institute, in magnetic birefringence in colloidal solutions of magnetic particles. 1907 detected both the Cotton -Mouton effect an intense magnetic induced birefringence having an optical axis parallel to the magnetic field lines.
In 1913 he married Eugénie Feytis, as a physicist. They had three children. During the Second World War, he and Pierre Weiss developed the Cotton -and-white system, with which one could detect enemy artillery.
He supervised the dissertation in 1914 by Georges Bruhat via circular dichroism and optical rotatory dispersion. In 1917, he helped the Institut d' optique théorique et appliquée (Institute of theoretical and practical optics) to establish, today the École supérieure d' optique. In 1914, he proposed the construction of a large electromagnet, which could generate magnetic fields. The work on the magnet finally began in 1924 in the service of the Recherches et inventions in Bellevue, later the Laboratoire du magnétisme in Meudon -Bellevue, which was eventually named in his honor Laboratoire Aimé Cotton. Magnetic fields up to 7 Tesla were produced.
In 1919, he was Chairman of the Physics Committee of the Direction des Inventions intéressant la défense national ( Directorate for inventions that are important for national defense ). In 1920 he was nominated as a professor for the new chair of theoretical physics and astrophysics at the Faculty of Sciences at the University of Paris. In 1922, he was followed by Gabriel Lippmann in the Department of General Physics and at the same time he was director of physical research at the faculty. In 1923 he was elected to the French Academy of Sciences, and in 1938 he became its president. He went into retirement in 1941 and was replaced by Jean Cabannes as a professor and laboratory director, although he retained the management of the magneto- optical laboratory in Bellevue. Also in 1941 he was captured by the German occupiers and was one and a half months in the prison of Fresnes. He was later awarded the Rosette de la Resistance ( rosette of resistance.) He died on 16 April 1951.