Orientational correlation functions and polarization selectivity for nonlinear spectroscopy of isotropic media. II. Fifth order

The influence of orientational relaxation on the fifth-order nonlinear polarization is evaluated for off-resonant Raman and dipole resonant experiments in the perturbative limit. The symmetry properties of the χ(5) tensor are discussed, and correlation functions for orientational diffusion are calculated for all fifth-order tensor elements relevant to isotropic media. The results allow generalization of the effect of orientational motion on the nonlinear experiment of arbitrary order. The general polarization dependence of the fifth-order experiments are obtained and used to address the selectivity of certain polarization geometries to orientational dynamics. It is shown that for χ(5) Raman spectroscopies, no combination of polarizations will give complete selectivity to the isotropic, anisotropic, or nonresonant contributions to the Raman polarizability tensor. Similar restriction of selectivity exists for resonant experiments. Polarization conditions are suggested to facilitate the comparison of third- and fifth-order spectroscopies.