Raman opalescence near the phase transition point in lead germanate crystals

Abstract

It was established that the nature of opalescence near the phase transition point in a lead germanate crystal is dynamic and is caused by a sharp increase in the spectral intensity of Raman scattering on a soft mode responsible for the instability of the crystal lattice near the phase transition temperature. Experimental studies of combination opalescence in a soft mode were performed using the method of constructing isofrequency temperature dependences of the spectral intensity for fixed values of the frequency shift Ω of the scattered radiation relative to the frequency ω0 of the exciting radiation. It is shown that the experimentally observed anomalies of the spectral intensity agree with the dynamic theory of phase transitions in crystals, based on the concept of softening of the crystal lattice in the phase transition region.