Max-Planck-Institut für Festkörperforschung, Stuttgart, D-70506, Germany;
Institut für Physik, Universität Augsburg, D-86135 Augsburg, Germany

We present a calculation of the Hg phonon self-energy for a model of A₃C₆₀ (A=K, Rb). The orientational disorder of the C₆₀ molecules is included, and the lowest order self-energy diagram is considered. The calculations illustrate that due to the violation of momentum conservation by the orientational disorder, Raman scattering can measure the decay of a phonon in an electron-hole pair, allowing the estimate of the electron-phonon coupling from such experiments. Comparison with experimental line shapes further provides support for a local correlation of the molecular orientations, with neighboring molecules preferentially having orientations differing by a 90 degrees rotation.

A reprint of this paper can be obtained from cond-mat in Germany or in the US.
 

Physical Review B, 60 6495-501, 1999.