Symmetry and magnetic vibrational circular dichroism spectra of a doubly degenerate vibration and its combinations with non-degenerate vibrational modes

Abstract

The role of symmetry in the A 1-term characteristics of magnetic vibrational circular dichroism spectra of molecules of D 4 (D 4h) and C 4v symmetry is discussed in order to derive a relationship between the, A 1/ D 0 ratios for a fundamental of a doubly degenerate vibration and certain combination transitions. It is demonstrated that the A 1/ D 0 ratio for the (e) fundamental is equal to those of (e+a 1) and (e+a 2) combination bands. For the (e+b 1) and (e+b 2) combination bands the ratios A 1/ D 0 were found to be equal in magnitude but of opposite sign to that of the fundamental. This behavior, which is largely model independent, is shown to result entirely from the symmetry of vibrations involved in the combination transitions.