Consideration of a frequency-independent damping coefficient from Raman measurements

The possibility of a frequency-independent or frequency-dependent damping constant is experimentally investigated, using the right-angle Raman results for the heavily damped soft-E mode in the ferroelectric PbTiO3 at 491°C (just below the transition temperature). The fits, over a wide frequency range, using a frequency-independent are so good that there is little room for any appreciable frequency dependence. This is in disagreement with several claims made in a recent paper by Heiman, Ushioda, and Remeika. © 1976 The American Physical Society.