The Thermo- optic Behaviour of Calcium Chloride and Ammonium Chloride and Zinc-Blende At Low Temperatures

Abstract

Using the data on the refraction at low temperatures given by Barbaron, the values of the proportionate shift with temperature of the ultraviolet dispersion frequencies (X = — 1/v dv/dt) of CaF2, NH4Cl and ZnS have been calculated and it has been found that the values of X tend to very low values near the absolute zero. In the case of ammonium chloride, a new dispersion formula has been proposed. In NH4 C1 and CaF2, the values of X for the dispersion frequencies obtained from thermooptic data are compared with the values of X of the lattice lines obtained from the temperature variation of the Raman spectra.