The application of high frequency thermal propagation data to the measurement of phonon relaxation times

The theory is developed of the propagation of high frequency thermal waves in dielectrics under circumstances in which phonons can undergo both normal and resistive interaction processes, each characterized by a frequency independent relaxation time. The first-order deviations from the classical results are examined in detail and it is suggested that measurement of these would allow independent estimates to be made of the normal and resistive process relaxation times. It is shown that present techniques should allow measurement of the effect to be conducted with reasonable accuracy.