Stability of clusters of fullerenes

We have studied the formation and stability of pure and mixed clusters of C ₆₀ and C ₆₀/C ₇₀ 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 (hv I.P.) followed by single photon ionisation with a F ₂ excimer laser. The stability patterns show features related to geometrical packing structures but much stronger than previously seen in cluster spectra. The fragmentation patterns for the mixed clusters indicate that C ₆₀ and C ₇₀ have similar binding energies in the clusters in contrast to what would be expected from vapour pressure data of macroscopic samples.