EXPERIMENTAL STUDIES OF FUSION AND FRAGMENTATION OF FULLERENES

Energy dependences of the fusion cross section for the collisions C-60 (+) + C-60, C-60(+) + C-70 and C-70(+) + C-70 have been measured. Fusi on occurs for energies above a sharp energetic barrier V-B. The fusion barrier lies in the region between 60 and 80 eV and increases with in creasing number of atoms participating in the collision. For energies beyond the barrier the fusion reaction cross section increases with co llision energy to a maximum value and then decreases very rapidly. The highly excited fusion compound decays on the experimental timescale, and the resulting fragmentation pattern has been studied as a function of collision energy. For energies up to 200 eV the fragmentation beha viour can be modelled in terms of successive evaporation of C-2 units from the hot fusion product. At higher energies this model breaks down and another fragmentation mechanism has to be invoked. The overall re sults are in very good agreement with quantum molecular dynamics simul ations and the predictions of simple phenomenological fusion models.