Rayleigh and Brillouin Scattering in RbH 3 (SeO 3 ) 2 near the Phase Transition Temperature

Rayleigh and Brillouin scattering spectra of RbH 3 (SeO 3 ) 2 have been observed around the phase transition temperature T C . The temperature dependence of the Brillouin frequency shifts shows a small anomaly near T C in all three principal directions. The sound-velocity dispersion is found only in the c 55 transverse mode. The intensity of the Rayleigh component is insensitive to temperature even just near T C . The existence of dynamic clusters above T C is discussed and its characteristic frequency is roughly estimated, while static clusters are concluded not to exist in the same temperature region.