Temperature dependence of Raman scattering spectra of internal modes in triglycine sulphate

Abstract

Micro-probed Raman scattering spectra of TGS have been observed above and below T_c with a special attention to internal modes. Several modes show anomalous behavior at T_c . The CH₂ symmetric stretching vibration splits into two modes below T_c . The temperature dependence of the frequency difference between these modes is in good agreement with that of the spontaneous polarization. The splitting indicates that the change of the environment of the molecule is strongly related to the order parameter in the phase transition.