Raman-scattering study of Ba-doped C60 with t1g states

Raman spectra are reported for Ba-doped fullerides BaxC60 (x = 3, 4, and 6). The lowest-frequency H-g modes split into five components for Ba4C60 and Ba6C60 even at room temperature, allowing us a quantitative analysis based on the electron-phonon coupling theory. For the superconducting Ba4C60, the density of states at the Fermi energy was derived as 7 eV(-1), while the total value of electron-phonon coupling lambda was found to be 1.0, which is comparable to that of K3C60. The tangential A(g)(2) mode, which is known as a sensitive probe for the degree of charge transfer on C-60 molecules, shows a remarkable shift depending on the Ba concentration, being roughly consistent with the full charge transfer from Ba to C-60. An effect of hybridization between Ba and C-60 pi orbitals is also discussed. [S0163-1829(99)01730-0].