Abstract
The linewidth and frequency of the and the optical lattice vibrations in quartz have been measured between 5 and 300°K by means of high-resolution Raman spectroscopy. The mode, which is both Raman- and infrared-active, is the lowest-lying optical vibration in quartz and shows a marked increase in lifetime at low temperatures. Utilizing available phonon dispersion spectra obtained from neutron scattering, the linewidth and shift are calculated in terms of three-phonon interactions. A simple model for the cubic anharmonicity, which includes relaxation broadening of the thermal phonons, is applied satisfactorily to the residual damping at low temperatures. The LO-TO splitting, which is extremely small, is not resolved directly, but manifests itself as an observed broadening at helium temperatures.
- Received 30 September 1968
DOI:https://doi.org/10.1103/PhysRev.178.1424
©1969 American Physical Society