RAMAN, ELECTRONIC RAMAN, INFRARED-ABSORPTION AND VISIBLE LUMINESCENCESPECTRUM OF CS2NAEUCL6

The 457.9 nm and 514.5 nm laser excited spectra of polycrystalline Cs2 NaEuCl6, at room temperature and 120 K are reported. The spectra are i nterpreted in terms of: (a) Raman transitions involving fundamental mo des of the EuCl63- moiety, with some features exhibiting different rel ative intensity as a function of excitation line; (b) Raman transition s involving lattice modes and combination bands with the phase transit ion soft mode; (c) electronic Raman bands of Eu3+; and (d) luminescenc e bands from the electronic and/or vibronic levels of (5D2)GAMMA3,GAMM A5, (5D1)GAMMA4 and (5D0)GAMMA1 to the electronic and/or vibronic leve ls of 7F(J) (J=0-6). The 120 K and 10 K infrared absorption spectra Of CS2NaEuCl6 are reported, and assigned in detail to the transitions in volving terminal crystal field and/or vibronic levels of 7F(J) (J=2-6) . A complete interpretation is given for the vibronic structure of the transitions. Together with the electronic Raman and luminescence resu lts, all of the energy levels of Eu3+ in Cs2NaEuCl6 up to 21 500 cm-1 have been assigned. At 120 K, the effects of the phase transition are not apparent from the moiety modes Of CS2NaEuCl6, but the caesium tran slational mode in the Raman spectrum is split. The degenerate electron ic levels exhibit splittings of up to several wavenumbers. A compariso n is made with the corresponding spectra of Cs2LiEuCl6, and a vibratio nal analysis is given for both compounds. The principal stretching for ce constant is about 10% greater in Cs2NaEuCl6 than in CS2LiEuCl6, whe reas the principal bending force constant is about 30% smaller.