Influence of temperature on the Raman spectra of crystals - Part I. Calcite
With the λ 2536 radiation of the mercury arc as exciter, the Raman spectrum of calcite has been studied at the temperatures 90°, 185°, 300°, 343°, 398°, 438°, 508°, 583°, 638° and 698° K. It is found thatall the Raman lines exhibit definite decrease in frequency shifts with increase in temperature, the decrease being much greater in the case of the lattice lines than in the internal oscillations of the CO3 group. The width of the Raman lines increases with temperature and this increase is of the same order of magnitude in each case as the diminution of frequency shift, the former being always greater than the latter. The temperature-frequency shift, and the temperature-width curves for the various. Raman lines exhibit a striking similarity in shape, tending to flatten up at low temperatures and the rate of change being greater at high temperature, suggesting a close relationship between the two. The peak intensity of the Raman lines is also found to decrease very much with rising temperature.