Absorption and magnetic circular dichroism spectra of Cs2ZrBr6: Os4+

High resolution absorption and magnetic circular dichroism (M.C.D.) spectra for Cs₂ZrBr₆ : Os⁴⁺ are reported at liquid helium temperature over the range 17 000–31 000 cm^-1. These results in conjunction with previous work on Cs₂ZrCl₆ : Os⁴⁺ provide a study of the Os⁴⁺ spectrum as a function of ligand spin-orbit coupling constant. The present results strongly support the previous ligand-to-metal charge-transfer interpretation formulated in the j-j limit, described by Piepho et al. [6]. The strong absorption bands can be assigned with confidence to specific, allowed charge-transfer transitions, and detailed assignments are suggested for the less intense features on the basis of forbidden (vibrationally-induced) charge-transfer transitions. Aside from the low energy region (? 16 000 cm^-1) not reported in this work, there seems to be no reason for assigning any important spectral features to d →d transitions.