Chapter 244 Magnetic Circular Dichroism of Lanthanides

Abstract

Abstract Magnetic circular dichroism (MCD) measures the difference in absorption of left and right circularly polarized light. MCD is complementary to the classical absorption technique but much more powerful as the experimental signals are characterized by a shape, a sign and a magnitude. The theory of absorption and MCD theory is discussed in detail with focus on subtle matters like: phase conventions, normalization, factors for randomly oriented molecules, dimention of quantities, sign properties…for both magnetic and induced electric dipole transitions. A special effort is made to establish the relationship between theoretical and experimental quantities and this is illustrated with examples pertaining to D2d, C4v, and D3h symmetry. The theory is adapted to the lanthanide spectroscopy formalism. Group theoretically it is shown that the shape and sign of the MCD signal give information on the coordination properties through selection rules for the induced electric dipole mechanism. The magnetic dipole transition 5D1 ⇆7F0 in Eu3 is proposed as a standard for scaling the MCD intensities. Finally the MCD spectra of aqueous solutions of ten lanthanide perchlorates are displayed together with the corresponding absorption spectra and transitions are listed with their full parameters.