Vibrational resonance coupling and the noncoincidence effect of the isotropic and anisotropic Raman spectral components in orientationally anisometric molecular liquids

Abstract

An expression for the splitting parameter associated with the noncoincidence of the peak positions of the polarized and depolarized Raman spectral components of a totally symmetric band in a molecular liquid has been derived. The derivation is based upon an angular dependent vibrational resonance coupling Hamiltonian, and has induced a more general interaction Hamiltonian than the induced dipole–induced dipole interaction. It has been shown that short-range orientational order is not essential for the noncoincidence effect, although the presence of short-range order can affect the magnitude of the splitting parameter. An example is given to show that the noncoincidence effect is not necessarily due to the induced dipole interaction mechanism. The present result shows that any angular dependent resonance coupling mechanism can give rise to the noncoincidence effect.