Induced contributions in the Rayleigh band of gaseous H₂O

Abstract

Isotropic and anisotropic induced contributions in light scattering from water vapour (418–453 K) along the liquid-vapour coexistence curve are studied. The evaluation of the induced effects takes into account the long range interactions described by the first few terms of the polarizability and multipolar series expansion. In performing the configurational averages at low density, different effective potentials in the literature are used and quantum corrections to the classical pair distribution function are considered. The quantum rotational-allowed spectrum is calculated and used to derive reliable intensities and lineshapes of the depolarized induced contributions. The role of the interference between rotational and translational variables (the cross-term) is discussed. The intensity and lineshape of the isotropic contributions are calculated and the theoretical frequency dependence of the depolarization ratio is compared with the experimental one.