Aimé Cotton
Encyclopedia
Aimé Auguste Cotton was a French physicist known for his studies of the interaction of light with chiral
molecules. In the absorption band
s of these molecules, he discovered large values of optical rotatory dispersion
(ORD), or variation of optical rotation as a function of wavelength (Cotton effect
), as well as circular dichroism
or differences of absorption between left and right circularly polarized light.
, Ain
on 9 October 1869. His grandfather was director of the École normale (teachers' college) of Bourg, and his father, Eugène Cotton, was a mathematics professor at the college of Bourg, the institution where physicist André-Marie Ampère
began his career. His brother Émile Cotton was a mathematician and academician.
Aimé Cotton attended a lycée (high school) in Bourg and then the special mathematics program at the Lycée Blaise Pascal
in Clermont-Ferrand
. He entered the École normale supérieure
in 1889, and won the physical sciences prize on graduating in 1893.
As a graduate student at the physics laboratory of the École normale supérieure, he then prepared his doctoral thesis in physical sciences. In this thesis he studied the interactions of polarized light with optically active substances containing chiral
molecules. In absorption
bands of these substances, he found large variations of optical rotation
as a function of wavelength, now known as optical rotatory dispersion
(ORD) or as the Cotton effect
.
He also discovered the related phenomenon of circular dichroism
, or unequal absorption of left and right circularly polarized light.
These two phenomena were later used to determine the stereochemistries
of chiral molecules in organic chemistry and in biochemistry.
He was appointed maître de conférences
in the science faculty at Toulouse
in 1895, and defended his doctoral thesis in 1896 before the science faculty of the University of Paris
. His thesis was entitled "Research on the absorption and dispersion of light by substances capable of optical rotation". In 1900, he was appointed assistant professor as a temporary replacement for Jules Violle
. In 1904 he was appointed instructor, and in 1910 assistant professor at the science faculty of the University of Paris, assigned to the École normale supérieure, where he remained until 1922.
During this period his research dealt with the interactions of light and magnetism
. He worked first with Pierre Weiss
on the Zeeman effect
, the splitting of spectral lines in the presence of a magnetic field
. For this work he invented the Cotton balance to measure the magnetic field intensity precisely. With Weiss he studied the magnetic splitting of the blue lines of the zinc
atom and in 1907 they were able to determine the ratio of the electron
's charge to its mass (e/m) with better precision than the method of J.J. Thomson.
Cotton then became interested in the Faraday effect
near absorption lines and demonstrated magnetic circular dichroism
. At the same time, he worked with his former classmate Henri Mouton
, a biologist at the Pasteur Institute
, on magnetic birefringence in colloïdal solutions of magnetic particles. In 1907 the two discovered the Cotton-Mouton effect
, an intense magnetic birefringence with optical axis parallel to the magnetic field lines.
In 1913 he married Eugénie Feytis, also a physicist. They had three children. During World War I
he and Pierre Weiss developed the Cotton-Weiss system for locating enemy artillery.
He supervised the thesis work of Georges Bruhat on circular dichroïsm and optical rotatory dispersion (1914). In 1917 he helped to found the Institut d'optique théorique et appliquée, now the École supérieure d'optique
. In 1914, he proposed construction of a large electromagnet
capable of producing intense magnetic fields. Work on the magnet finally started in 1924 in the Service des recherches et inventions at Bellevue, later the Laboratoire du magnétisme at Meudon-Bellevue, and finally the Laboratoire Aimé Cotton in his honour. Magnetic fields as high as to 7 teslas
were attained.
In 1919, he became chairman of the physics committee of the Direction des Inventions intéressant la défense nationale (Directorate of Inventions relevant to National Defense). In 1920 he was named professor of the new chair of theoretical physics and astrophysics at the Faculty of Sciences of the University of Paris
. In 1922 he succeeded Gabriel Lippmann
in the chair of general physics, and at the same time became director of physics research in the faculty. In 1923 he was elected to the French Academy of Sciences
, and in 1938 he was elected its president. He retired in 1941 and was replaced by Jean Cabannes
as professor and laboratory directory, although he retained the direction of the magneto-optics laboratory at Bellevue. Also in 1941 he was imprisoned by the German occupiers at Fresnes
for one and a half months, and was later awarded the Rosette de la résistance. He died on April 16, 1951 at Sèvres
.
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
molecules. In the absorption band
Absorption band
An absorption band is a range of wavelengths, frequencies or energies in the electromagnetic spectrum which are able to excite a particular transition in a substance...
s of these molecules, he discovered large values of optical rotatory dispersion
Optical rotatory dispersion
Optical rotatory dispersion is the variation in the optical rotation of a substance with a change in the wavelength of light. Optical rotatory dispersion can be used to find the absolute configuration of metal complexes....
(ORD), or variation of optical rotation as a function of wavelength (Cotton effect
Cotton effect
The Cotton effect is the characteristic change in optical rotatory dispersion and/or circular dichroism in the vicinity of an absorption band of a substance....
), as well as circular dichroism
Circular dichroism
Circular dichroism refers to the differential absorption of left and right circularly polarized light. This phenomenon was discovered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton in the first half of the 19th century. It is exhibited in the absorption bands of optically active chiral...
or differences of absorption between left and right circularly polarized light.
Biography
Aimé Cotton was born in Bourg-en-BresseBourg-en-Bresse
Bourg-en-Bresse is a commune in eastern France, capital of the Ain department, and was capital of the former province of Bresse . It is located north-northeast of Lyon.The inhabitants of Bourg-en-Bresse are known as Burgiens.-Geography:...
, Ain
Ain
Ain is a department named after the Ain River on the eastern edge of France. Being part of the region Rhône-Alpes and bordered by the rivers Saône and Rhône, the department of Ain enjoys a privileged geographic situation...
on 9 October 1869. His grandfather was director of the École normale (teachers' college) of Bourg, and his father, Eugène Cotton, was a mathematics professor at the college of Bourg, the institution where physicist André-Marie Ampère
André-Marie Ampère
André-Marie Ampère was a French physicist and mathematician who is generally regarded as one of the main discoverers of electromagnetism. The SI unit of measurement of electric current, the ampere, is named after him....
began his career. His brother Émile Cotton was a mathematician and academician.
Aimé Cotton attended a lycée (high school) in Bourg and then the special mathematics program at the Lycée Blaise Pascal
Blaise Pascal
Blaise Pascal , was a French mathematician, physicist, inventor, writer and Catholic philosopher. He was a child prodigy who was educated by his father, a tax collector in Rouen...
in Clermont-Ferrand
Clermont-Ferrand
Clermont-Ferrand is a city and commune of France, in the Auvergne region, with a population of 140,700 . Its metropolitan area had 409,558 inhabitants at the 1999 census. It is the prefecture of the Puy-de-Dôme department...
. He entered the École normale supérieure
École normale supérieure
An école normale supérieure or ENS is a type of publicly funded higher education in France. A portion of the student body who are French civil servants are called Normaliens....
in 1889, and won the physical sciences prize on graduating in 1893.
As a graduate student at the physics laboratory of the École normale supérieure, he then prepared his doctoral thesis in physical sciences. In this thesis he studied the interactions of polarized light with optically active substances containing chiral
Chirality (chemistry)
A chiral molecule is a type of molecule that lacks an internal plane of symmetry and thus has a non-superimposable mirror image. The feature that is most often the cause of chirality in molecules is the presence of an asymmetric carbon atom....
molecules. In absorption
Absorption spectroscopy
Absorption spectroscopy refers to spectroscopic techniques that measure the absorption of radiation, as a function of frequency or wavelength, due to its interaction with a sample. The sample absorbs energy, i.e., photons, from the radiating field. The intensity of the absorption varies as a...
bands of these substances, he found large variations of optical rotation
Optical rotation
Optical rotation is the turning of the plane of linearly polarized light about the direction of motion as the light travels through certain materials. It occurs in solutions of chiral molecules such as sucrose , solids with rotated crystal planes such as quartz, and spin-polarized gases of atoms...
as a function of wavelength, now known as optical rotatory dispersion
Optical rotatory dispersion
Optical rotatory dispersion is the variation in the optical rotation of a substance with a change in the wavelength of light. Optical rotatory dispersion can be used to find the absolute configuration of metal complexes....
(ORD) or as the Cotton effect
Cotton effect
The Cotton effect is the characteristic change in optical rotatory dispersion and/or circular dichroism in the vicinity of an absorption band of a substance....
.
He also discovered the related phenomenon of circular dichroism
Circular dichroism
Circular dichroism refers to the differential absorption of left and right circularly polarized light. This phenomenon was discovered by Jean-Baptiste Biot, Augustin Fresnel, and Aimé Cotton in the first half of the 19th century. It is exhibited in the absorption bands of optically active chiral...
, or unequal absorption of left and right circularly polarized light.
These two phenomena were later used to determine the stereochemistries
Stereochemistry
Stereochemistry, a subdiscipline of chemistry, involves the study of the relative spatial arrangement of atoms within molecules. An important branch of stereochemistry is the study of chiral molecules....
of chiral molecules in organic chemistry and in biochemistry.
He was appointed maître de conférences
Academic rank in France
The following summarizes basic academic ranks in the French higher education system:-State university system:* PU equivalent to Full Professor)...
in the science faculty at Toulouse
Toulouse
Toulouse is a city in the Haute-Garonne department in southwestern FranceIt lies on the banks of the River Garonne, 590 km away from Paris and half-way between the Atlantic Ocean and the Mediterranean Sea...
in 1895, and defended his doctoral thesis in 1896 before the science faculty of the University of Paris
University of Paris
The University of Paris was a university located in Paris, France and one of the earliest to be established in Europe. It was founded in the mid 12th century, and officially recognized as a university probably between 1160 and 1250...
. His thesis was entitled "Research on the absorption and dispersion of light by substances capable of optical rotation". In 1900, he was appointed assistant professor as a temporary replacement for Jules Violle
Jules Violle
Jules Louis Gabriel Violle was a French physicist and inventor.He is notable for having determined the solar constant at Mont Blanc in 1875, and, in 1881, for proposing a standard for luminous intensity, called the Violle, equal to the light emitted by 1 cm² of platinum at its melting point...
. In 1904 he was appointed instructor, and in 1910 assistant professor at the science faculty of the University of Paris, assigned to the École normale supérieure, where he remained until 1922.
During this period his research dealt with the interactions of light and magnetism
Magnetism
Magnetism is a property of materials that respond at an atomic or subatomic level to an applied magnetic field. Ferromagnetism is the strongest and most familiar type of magnetism. It is responsible for the behavior of permanent magnets, which produce their own persistent magnetic fields, as well...
. He worked first with Pierre Weiss
Pierre Weiss
Pierre-Ernest Weiss was a French physicist who developed the domain theory of ferromagnetism in 1907. Weiss domains and the Weiss magneton are named after him. Weiss also developed the Molecular or Mean field theory, which is often called Weiss-mean-field theory.Weiss was born in Mulhouse and...
on the Zeeman effect
Zeeman effect
The Zeeman effect is the splitting of a spectral line into several components in the presence of a static magnetic field. It is analogous to the Stark effect, the splitting of a spectral line into several components in the presence of an electric field...
, the splitting of spectral lines in the presence of a magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
. For this work he invented the Cotton balance to measure the magnetic field intensity precisely. With Weiss he studied the magnetic splitting of the blue lines of the zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
atom and in 1907 they were able to determine the ratio of the electron
Electron
The electron is a subatomic particle with a negative elementary electric charge. It has no known components or substructure; in other words, it is generally thought to be an elementary particle. An electron has a mass that is approximately 1/1836 that of the proton...
's charge to its mass (e/m) with better precision than the method of J.J. Thomson.
Cotton then became interested in the Faraday effect
Faraday effect
In physics, the Faraday effect or Faraday rotation is a Magneto-optical phenomenon, that is, an interaction between light and a magnetic field in a medium...
near absorption lines and demonstrated magnetic circular dichroism
Magnetic circular dichroism
Magnetic circular dichroism is the differential absorption of left and right circularly polarized light, induced in a sample by a strong magnetic field oriented parallel to the direction of light propagation...
. At the same time, he worked with his former classmate Henri Mouton
Henri Mouton
Henri Mouton [5 September 1869, Cambrai - 13 June 1935, Bezons ] was a French scientist.He entered the École normale supérieure in 1889. He was a biologist at the Institut Pasteur, then...
, a biologist at the Pasteur Institute
Pasteur Institute
The Pasteur Institute is a French non-profit private foundation dedicated to the study of biology, micro-organisms, diseases, and vaccines. It is named after Louis Pasteur, who made some of the greatest breakthroughs in modern medicine at the time, including pasteurization and vaccines for anthrax...
, on magnetic birefringence in colloïdal solutions of magnetic particles. In 1907 the two discovered the Cotton-Mouton effect
Cotton-Mouton effect
In physical optics, the Cotton–Mouton effect refers to the double refraction of light in a liquid in the presence of a constant transverse magnetic field. It is a similar but stronger effect than the Voigt effect...
, an intense magnetic birefringence with optical axis parallel to the magnetic field lines.
In 1913 he married Eugénie Feytis, also a physicist. They had three children. During World War I
World War I
World War I , which was predominantly called the World War or the Great War from its occurrence until 1939, and the First World War or World War I thereafter, was a major war centred in Europe that began on 28 July 1914 and lasted until 11 November 1918...
he and Pierre Weiss developed the Cotton-Weiss system for locating enemy artillery.
He supervised the thesis work of Georges Bruhat on circular dichroïsm and optical rotatory dispersion (1914). In 1917 he helped to found the Institut d'optique théorique et appliquée, now the École supérieure d'optique
École supérieure d'optique
The École supérieure d'optique , nicknamed "SupOptique", is the leading French grande école in the field of optics and its industrial and scientific applications, and a member of the prestigious UniverSud Paris and ParisTech...
. In 1914, he proposed construction of a large electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
capable of producing intense magnetic fields. Work on the magnet finally started in 1924 in the Service des recherches et inventions at Bellevue, later the Laboratoire du magnétisme at Meudon-Bellevue, and finally the Laboratoire Aimé Cotton in his honour. Magnetic fields as high as to 7 teslas
Tesla (unit)
The tesla is the SI derived unit of magnetic field B . One tesla is equal to one weber per square meter, and it was defined in 1960 in honour of the inventor, physicist, and electrical engineer Nikola Tesla...
were attained.
In 1919, he became chairman of the physics committee of the Direction des Inventions intéressant la défense nationale (Directorate of Inventions relevant to National Defense). In 1920 he was named professor of the new chair of theoretical physics and astrophysics at the Faculty of Sciences of the University of Paris
University of Paris
The University of Paris was a university located in Paris, France and one of the earliest to be established in Europe. It was founded in the mid 12th century, and officially recognized as a university probably between 1160 and 1250...
. In 1922 he succeeded Gabriel Lippmann
Gabriel Lippmann
Jonas Ferdinand Gabriel Lippmann was a Franco-Luxembourgish physicist and inventor, and Nobel laureate in physics for his method of reproducing colours photographically based on the phenomenon of interference....
in the chair of general physics, and at the same time became director of physics research in the faculty. In 1923 he was elected to the French Academy of Sciences
French Academy of Sciences
The French Academy of Sciences is a learned society, founded in 1666 by Louis XIV at the suggestion of Jean-Baptiste Colbert, to encourage and protect the spirit of French scientific research...
, and in 1938 he was elected its president. He retired in 1941 and was replaced by Jean Cabannes
Jean Cabannes
Jean Cabannes was a French physicist specialising in optics.From 1910 to 1914 Cabannes worked in the laboratory of Charles Fabry in Marseille on the topic launched by Lord Rayleigh at the end of the 19th century of how gas molecules diffused light. In 1914 he showed that pure gases could scatter...
as professor and laboratory directory, although he retained the direction of the magneto-optics laboratory at Bellevue. Also in 1941 he was imprisoned by the German occupiers at Fresnes
Fresnes Prison
Fresnes Prison is the second largest prison in France, located in the town of Fresnes, Val-de-Marne South of Paris...
for one and a half months, and was later awarded the Rosette de la résistance. He died on April 16, 1951 at Sèvres
Sèvres
Sèvres is a commune in the southwestern suburbs of Paris, France. It is located from the centre of Paris.The town is known for its porcelain manufacture, the Manufacture nationale de Sèvres, making the famous Sèvres porcelain, as well as being the location of the International Bureau of Weights...
.