RAMAN-SPECTRA OF (LIRBSO4)-LI-6 AND (LIRBSO4)-LI-7

Abstract

The polarized Raman spectra of single-crystal (LiRbSO4)-Li-6 and (LiRbSO4)-Li-7 at room temperature are reported. On the basis of these data, symmetry-based band assignments are given for both internal and external optic modes. The translational optic modes of the lithium ion appear in the region between 444 and 364 cm-1. Vibrational coupling interactions are noted between the sulfate ion nu2 and the lithium translational optic modes in the same irreducible representation. Coupling interactions are negligible or small in (LiRbSO4)Li-7, while in (LiRbSO4)-Li-6 the lithium isotope effect shifts the lithium translational modes into more coupling interaction with the sulfate ion nu2 modes.