Decay of high-frequency longitudinal phonons

Abstract

The anharmonic decay of a high-frequency longitudinal elastic wave at low temperatures, such that ℏω> KT, is calculated by perturbation theory, using a Grüneisen parameter as measure of the anharmonicity. The attenuation at very low temperatures varies as the fifth power of frequency, and is small at frequencies below 1012 Hz. © 1967 The American Institute of Physics.