Electronic properties of Ba-intercalated fullerides

Raman spectra have been measured on BaxC60 binary systems for x=3, 4 and 6. The pentagonal pinch Ag(2) mode exhibits a softening in an approximately p roportional manner to the formal valence of C-60 molecule. This result sugg ests that the valence of C-60 in Ba doped systems are understood by the nai ve ionic crystal model based on Ba2+. The broader Raman peaks in supercondu cting Ba4C60 indicates that the electron-phonon interaction is considerably large comparing to those for Ba3C60 and Ba6C60.