https://doi.org/10.1351/goldbook.MT06778
Magnetic circular @DT07357@ is observed when a sample differentially absorbs left- and right- circularly polarized light in a magnetic field parallel to the light beam.
Notes:
- The MCD signal, \(\Delta\), is calculated as \[\Delta = \frac{\alpha(\lambda)^{-}\,-\,\alpha(\lambda)^{+}}{\alpha(\lambda)^{-}\,+\,\alpha(\lambda)^{+}}\] with \(\alpha(\lambda)^{-}\) and \(\alpha(\lambda)^{+}\) the absorption coefficients for right and left circularly polarized light, respectively. The spectra are a representation of \(\Delta\) vs @W06659@. Often, \(\Delta\) is recorded as a function of the applied field (up to \(10\ \text{T}\)) and the temperature.
- Phenomenon related to 'magnetically induced @O04303@ (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 @D01668@, @P04404@ and (@A00381@)-ferromagnetic material and has been observed from IR (@IT07399@) 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-@Z06739@) or (ii) states are mixed together by the applied magnetic field (second-order-@Z06739@). This may occur in the initial or the final states.
- 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 @W06659@ dependence of MCD can be used also to identify and assign optical transitions from metal ion sites.
- Technique complementary to both EPR and electronic absorption spectroscopies in facilitating assignment of the ground-state spin and electronic transitions of a molecular entity.