Raman spectroscopy of undoped and doped single crystal C60

We present high resolution Raman spectra of undoped single crystals at low temperatures using laser exitations in the red and green spectral range. A splitting of the Hg modes in Ag, Eg and Fg modes was found. A maximum of 8 splitted components could be observed. ping of the single crystals with potassium was performed at temperatures slightly above room temperature and the doping process was studied by using in-situ Raman spectroscopy. Up to the penetration depth of the laser homogeneous single phases of K1C60 and K3C60 could be obtained. At cooling the high temperature phase K1C60 was observed to undergo a sharp transition into C60 and K3C60 between 430 K and 410 K. In addition temperature dependent Raman measurements were performed on single phase K3C60. At liquid nitrogen temperature an unexpected strong splitting and selective line broadening of the Hg modes was observed which can be discussed in a model of single particle excitation interaction.