Raman line shapes in A3C60 (A = K, Rb): effects of orientational disorder on phonon spectra.

Gunnarsson O., Han J. E.

Max-Planck-Institut für Festkörperforschung, Stuttgart, D-70506, Germany

The authors calc. the Hg phonon self-energy for a model of A3C60 (A = K, Rb) using the lowest order self-energy diagram. The model includes the orientational disorder of the C60 mols. in A3C60 compds. Due to the violation of momentum conservation by the orientational disorder, even q = 0 phonons can very effectively decay in electron-hole pairs. This leads to an addnl. broadening of these phonons in metallic systems, which can be measured in Raman spectroscopy. The measured addnl. broadening provides an est. of the electron-phonon coupling. Comparison with exptl. line shapes further provides support for a local correlation of the mol. orientations, with neighboring mols. preferentially having orientations differing by a 90.degree. rotation.

in: Recent advances in the chemistry and physics of fullerenes and related materials. Eds. P. V. Kamat, D. M. Guldi, K. M. Kadish. Pennington, N. J. (1999), 588-596 (Proceedings Vol. 99-12. The Electrochemical Society).

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