Phase transition mechanisms revealed by optical spectroscopy

Abstract

Light scattering provides a powerful tool for analysing the spectrum of lattice vibrations with respect to structural transformations. Characteristic aspects are reviewed shortly. Recent results of Brillouin and Raman investigations referring to the transitions of Rochelle salt and ammonium sulfate are presented. The elastic anomalies of these systems in the frequency range of acoustical phonons are discussed and the coupling of the order parameters to lattice vibrations is investigated.