PLASMON DISPERSION AND BROADENING IN A(3)C(60) (A=K,RB)

Inelastic electron energy loss measurements of the 0.5-eV charge carri er plasmon in K3C60 are presented, showing that the plasmon has a very large broadening but a negligible dispersion. The response function i s calculated in a self-consistent, conserving approximation, showing t hat the plasmon broadening can be explained in terms of a decay in an electron-hole pair dressed by phonons. The plasmon dispersion can be u nderstood within the random-phase approximation. Local-field effects t end to give a large negative dispersion, which is compensated by inter band effects.