Preferred Label : magnetic circular dichroism;
IUPAC acronym : MCD; EPR; IR;
IUPAC definition : Magnetic circular dichroism is observed when a sample differentially absorbs left-
and right- circularly polarized light in a magnetic field parallel to the light beam.;
Scope note : phenomenon related to magnetically induced optical activity (faraday effect) by the
kramers-kronig transformations, which connect optical refraction and absorption, i.e.,
mcd is observed in optically active materials at wavelengths with non-vanishing absorption.
it occurs for diamagnetic, paramagnetic and (anti)-ferromagnetic material and has
been observed from ir (infrared) to x-ray regions. mcd optical transitions in molecular
species arise if (i) degenerate electronic states are split in the presence of a magnetic
field (first-order-zeeman effect) or (ii) states are mixed together by the applied
magnetic field (second-order-zeeman effect). this may occur in the initial or the
final states.; the mcd signal,d, is calculated as d a¿ -
a¿ a¿ - a¿
with a¿ - and a¿ the absorption coefficients for right and left
circularly polarized light, respectively. the spectra are a representation of d vs
wavelength. often, d is recorded as a function of the applied field (up to 10t) and
the temperature.; technique complementary to both epr and electronic absorption spectroscopies in facilitating
assignment of the ground-state spin and electronic transitions of a molecular entity.; mcd is used as a probe of paramagnetism that permits the identification of the electronic
and magnetic properties of the ground states of transition metal ion centres. the
wavelength dependence of mcd can be used also to identify and assign optical transitions
from metal ion sites.;
Origin ID : MT06778;
Automatic exact mappings (from CISMeF team)
- See also
Magnetic circular dichroism is observed when a sample differentially absorbs left-
and right- circularly polarized light in a magnetic field parallel to the light beam.
