Isotropic Raman scattering for non-totally symmetric vibrations of correlated molecules with intrinsic optical anisotropy

The mechanism of isotropic Raman scattering for non-totally symmetric vibrations, forbidden in the absence of molecular correlations, is analyzed. It is shown that long-range molecular electric fields within the dipole–induced dipole model (DID) lead to isotropic Raman scattering in this case. By Racah algebra, the isotropic parts of the effective Raman polarizability and the intensity of scattered light are examined. The magnitude of this effect for the A2 vibration of the water molecule is estimated. It is shown that the order of this effect is the same as that of collision-induced depolarized Raman scattering for symmetric vibrations of optically isotropic molecules.