The Cotton effect in
physics
Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...
, is the characteristic change in
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. For example, when plane-pol ...
and/or
circular dichroism in the vicinity of an
absorption band of a substance.
In a wavelength region where the light is absorbed, the absolute magnitude of the
optical rotation at first varies rapidly with wavelength, crosses zero at absorption maxima and then again varies rapidly with wavelength but in the opposite direction. This phenomenon was discovered in 1895 by the French physicist
Aimé Cotton
Aimé Auguste Cotton (9 October 1869 – 16 April 1951) was a French physicist known for his studies of the interaction of light with chiral molecules. In the absorption bands of these molecules, he discovered large values of optical rotator ...
(1869–1951).
The Cotton effect is called ''positive'' if the optical rotation first increases as the wavelength decreases (as first observed by Cotton), and ''negative'' if the rotation first decreases.
A protein structure such as a
beta sheet shows a negative Cotton effect.
See also
*
Cotton–Mouton effect
References
Polarization (waves)
Atomic, molecular, and optical physics
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