Dynamic Central Peaks in a Crystalline Solid: KTaO3

Use of a computer-assisted normalization procedure and a resonant reabsorption technique has permitted frequency resolution of two central peaks in the quasielastic-light-scattering spectrum of KTa${\mathrm{O}}_3$ in the 0 to 3 ${\mathrm{cm}}^{-1\mathrm{}}$ range. The intensities, and the polarization, temperature, electric field, and angular dependences of the linewidths indicate that the narrow component (2.3±0.3 GHz at 300 K in right-angle scattering) is due to entropy fluctuations. A tentative identification of the broader component with two-phonon processes is made.