ISOTROPIC AND ANISOTROPIC RAMAN-SCATTERING FROM MOLTEN LICL-CSCL MIXTURES - COMPOSITION AND TEMPERATURE EFFECTS

Molten mixtures of lithium chloride and cesium chloride have been stud ied using Raman spectroscopy at temperatures up to 850 degrees C. Redu ced isotropic and anisotropic Raman relative intensities have been mea sured at different compositions and temperatures. The spectra of the m ixtures show two bands with ''characteristic'' frequencies omega(Cs) a nd omega(Li) close to the frequencies of the bands of the pure compone nts. Both omega(Cs) and omega(Li) shift to higher energies with increa sing mole fraction of CsCl and LiCl, respectively. The scattering inte nsity spectra of the mixtures are compared with the simulated additive spectra of the component salts, Increasing temperature increases dras tically the isotropic intensity of the omega(Li) band but has minor ef fects on the anisotropic intensities. The data are discussed and inter preted in terms of interaction-induced polarizability fluctuations. Sh ort range overlap interactions, mainly between Li+ and Cl-, and the '' symmetry'' of the local structure around the anion determine the breat hing-like fluctuations which contribute to isotropic scattering and ac count for the drastic temperature and composition dependence of the Ra man intensities. The main contribution to anisotropic scattering arise s from near-neighbor dipole-induced-dipole interactions between the hi ghly polarized Cs+ and Cl- ions. (C) 1996 American Institute of Physic s.