Carbon clusters revisited: The ‘‘special’’ behavior of C60 and large carbon clusters

We have performed a series of experiments in which the conditions necessary for synthesis and detection of carbon clusters have been systematically investigated. The effects of ionizing laser intensity and frequency, vaporization and condensation conditions, and graphite substrate composition (pure and metal loaded) on the carbon cluster ion signals show that ‘‘special’’ conditions are needed to observe locally enhanced ion signals on particular clusters (e.g., a large C+60 signal). We present evidence for two sources of carbon clusters, one source which produces mostly smaller (n 32) carbon clusters. In addition we find that several, not just one, metal atom can be attached to C60. Lastly we propose that large variations in ion signals may be explained in terms of the electronic properties of the carbon clusters.