VIBRATIONAL STUDIES OF THE OXYSULFIDE (LAO)4GAS4.5

Far-infrared and Raman spectra of the oxysulphide (LaO)4GaS4.5 single crystal were measured and analysed. The interpretation of the observed spectra is based on the existence of (S-S)2-disulphur groups which ar e responsible for the high-frequency features. Most of the frequencies are assigned in terms of internal and external vibrations of tetrahed ral La4O groups, GaS4 units and (S-S)2-disulphur groups. Spectroscopy measurements are in good agreement with the recent structure determina tion.