Raman spectra of the second order in crystals Part IV. Barytes

The previous work on the Raman effect in barytes has been briefly reviewed. The Raman effect in natural crystals of barytes has been studied in detail using the 2536.5 λ mercury resonance radiation as exciter. The recorded spectrum consists of not less than 39 Raman lines nearly half of which have been recorded for the first time. Of these 20 lines belong to the first order Raman spectrum and are distributed as follows:-9 lattice lines and 11 lines due to the internal oscillations of the SO4 ion. The frequency shifts of these lines have been accurately measured. The appearance of 11 Raman lines in the first order spectrum of the SO4 ion has been satisfactorily explained on the basis of the lower order of symmetry of barytes crystal and also due to Fermi resonance splitting. 19 Raman lines of comparatively feeble intensity which constitute the second order spectrum have been assigned as octaves and combinations of some of the 20 principal Raman frequencies. The frequencies corresponding to the maxima observed in the infra-red absorption spectrum of barytes have been compared with those observed in the Raman effect. A complete bibliography on the Raman effect and infra-red studies in barytes is included