The Raman spectra of alkali halide melts: A theoretical description

A theoretical description of the light scattering (Raman) spectra of molten salts is presented. Expressions are derived to relate the spectra of the fluctuating polarizability induced by the ion Coulomb field and by the dipole–induced dipole mechanism to the spectra of the mass and charge density fluctuations (i.e., the dynamical structure factors). The theory thereby connects the spectral features seen in light scattering to well known dynamical processes in the ionic melt, such as the charge density wave (plasmon) and the ionic diffusive motion. The validity of this description is confirmed by evaluating the theoretical expression, using dynamical structure factors calculated in computer simulations, and comparing it with spectra calculated directly from the simulations.