A microscopic reason of the opalescence phenomenon observed earlier near the α–β phase transition point at 846 K in crystalline quartz is established. It was shown that the opalescence in quartz crystals is of dynamic nature and results from a sharp increase of Raman scattering spectral intensity (Raman opalescence phenomenon) due to huge fluctuations of the destabilizing soft mode responsible for instability of the crystalline lattice. The Raman opalescence of a destabilizing soft mode is estimated experimentally in the x (zz)y light scattering geometry by recording temperature dependencies of spectral Raman intensity I(ω′,T) (ω′=ω0‐Ω=const) at fixed frequencies ω′. The strong intensity increase of Raman scattering intensity (Raman opalescence) observed at the exact phase‐transition temperature in crystalline quartz is explained by taking into account interaction of the destabilizing soft mode with a low‐frequency high‐finesse oscillator.
The Raman opalescence of an effective soft mode in crystalline lead germanate is investigated. Recording of Raman scattering intensity was in the x (zz)y geometry corresponding to the soft mode, responsible for ferroelectric phase transition point at 451 K. The Raman spectra were measured at fixed temperatures T (I(ω′, T); T = const) and also at fixed wavenumbers ω′ of Raman spectrometer (I(ω′, T); ω′ = ω0 – Ω = const) with slow temperature changing. The strong increase of Raman scattering intensity (Raman opalescence) has been observed at temperatures of phase transition region. The appearance of central peak scattering is attributed to the strong interaction of the effective soft mode with a low‐wavenumber nonfundamental oscillator.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.