A model for rotational relaxation and resonance

Abstract

Depolarized Rayleigh and Raman scattering and far infrared absorption has revealed the rotational motion of polar molecules in liquids. The presence of both a Debye relaxation spectrum and a broad resonance indicates that the molecules oscillate and in addition are subject to some sort of relaxation mechanism. A model is proposed in which the molecule oscillates in a potential well until thermal fluctuations cause it to surpass the potential barrier and jump to a neighbouring well. For two-dimensional rotation approximate analytic expressions are obtained for the spectrum, which agree qualitatively with the measurements. The conclusion is that both resonance and relaxation can be obtained from a single mechanism, so that it is not necessary to introduce one mechanism for each of them.

Additional information

Notes on contributors

N.G. van Kampen

On leave of absence from the Institute for Theoretical Physics of the University at Utrecht, Netherlands.