c © Springer-Verlag 1997 Stability of clusters of fullerenes

Abstract. We have studied the formation and stability of pure and mixed clusters of C60 and C60=C70 produced in a gas aggregation source. The source yields very smooth abundance distributions indicating an efficient cooling. The stability of the clusters was probed by varying the degree of heating with a XeCl excimer laser (h < I:P:) followed by single photon ionisation with a F2 excimer laser. The sta-bility patterns show features related to geometrical packing structures but much stronger than previously seen in cluster spectra. The fragmentation patterns for the mixed clusters in-dicate that C60 and C70 have similar binding energies in the clusters in contrast to what would be expected from vapour pressure data of macroscopic samples. PACS: 36.40.+d