Spectral intensities in cubic systems. II. The MoCl63- system in cubic elpasolite crystals

Abstract

The visible and near infrared luminescence spectra of MoCl63- in Cs2NaMCl6 (M=Sc, Y, ln) and MoBr63- in Cs2NaYBr6 have been reported between 15 000 cm-1 and 3000 cm-1 at liquid helium temperatures. It has been observed that each electronic transition shows an extensive and rich vibronic structure, which can be analysed to yield the vibrational frequencies of the MoX63- ion in each electronic state. A through analysis of the spectra for these systems, show that the vibrational frequencies associated with each of the electronic transition is almost identical. This is an evidence of a weak or rather negligible Jahn-Teller distorsions. The spectra though are strongly influenced by resonant interactions among the MoX63- ion and the internal and lattice modes of the host lattices and there is also a noticeable variation of the relative vibronic distributions of parity forbidden transitions assisted by the odd parity normal modes of vibrations. This present work deals with the most likely int