MAGNETIC CIRCULAR DICHROISM IN THE LAHTHANIDES. I.
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Date
1975
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Publisher
Ohio State University
Abstract
Magnetic circular dichroism (MCD) is expressed $theoretically^{1}$ by $\Delta k = (k^{-} - k_{+}) = \{A f_{1} + (B + C/kT) f_{0}$\} H. A-terms originate in ground or excited state degeneracy, B-terms represent first order mixing states by the field, and C-terms arise from ground state population differences; $f_{0}$ and $f_{1}$ are the zeroth and first derivatives of the line shape, and H is the applied field. The Laporte-forbidden transitions in the lanthanides are known to result from breakdown in parity induced by odd order contributions to the crystal field Hamiltonian (``forced electric-dipole transitions”), and have been successfully treated in absorption by $Judd^{2}$ and $Ofclt.^{3}$ He extend their theory to MCD. Due to the narrow line widths and highly paramagnetic nature of the lanthanides, the MCD is generally dominated by Large A terms, Whereas positive A terms are predicted for the allowed transitions, both positive and negative A terms are observed for the “forced electric-dipole transitions”. The sign of the MCD correlates in a simple fashion with the relative magnitudes of the various odd order terms in the crystal field potential.
Description
$^{1}$P. J. Stephens, J. Chem. Phys, 52, 3489 (1970). $^{2}$B. R. Judd, Phys. Rev, 127, 750 (1962). $^{3}$G. S, Ofelt, J. Chem. Phys. 37, 511 (1962).""
Author Institution: Department of Chemistry, Syracuse University
Author Institution: Department of Chemistry, Syracuse University