RAMAN-SCATTERING IN K4C60 AND RB4C60 FULLERENES

Raman-scattering measurements have been performed in situ in ultrahigh vacuum on A4C60 (A=Rb,K) body-centered-tetragonal films prepared by sublimation of alkali metals from A6C60. The polarized and depolarized spectra indicate substantial broadening of tangential Hg modes as well as large disorder-induced radial-mode scattering. Alkali-metal local-site disorder due to either compositional fluctuations or site displacements are suggested. This disorder, in addition to electron-correlation effects, is expected to influence the nonmetallic nature of these materials. Variations in Hg mode frequencies and widths for all x values emphasize radial-mode electron-phonon damping for x=3. © 1995 The American Physical Society.