MEV ATOMIC ION SPUTTERING OF FULLERENES - A RADIAL-VELOCITY DISTRIBUTION STUDY

We report swift heavy-ion-induced sputtering of carbon cluster ions fr om fullerene-containing and polymer thin films (pure C-60, fluorinated C-60(C60Fm, 24 < m < 48), blends of pure C-60 With polystyrene (PS/C- 60), and poly(vinylidene fluoride) (PVDF)). Intact C-60 molecular ions and their fragments (C-60-2n, 1 < n < 5), together with a series of h igher mass carbon cluster ions (C-60+2n, n from 1 to at least 100) are ejected as a result of the interaction of an individual MeV ion with the various targets. The intensity patterns of the higher mass carbon cluster ion series depend on the type of bombarded target. For pure C- 60 targets the high mass clusters have higher yields around multiples of 60 (C-120 and C-180). In the case of PS/C-60, C-60 F-m and PVDF tar gets, the cluster intensity decreases continuously with increasing clu ster size. Measurements of the initial radial velocity distributions o f such cluster ions have been performed in a reflectron time-of-flight mass spectrometer, using 72.3 MeV I-127(13+) as primary ions. The rad ial velocity distributions of the sputtered ions are indicative of the processes of their formation: condensation of hot carbon atom ''gas'' in the core of the ion tracks versus coalescence of C-60 molecules, m ost probably in the gas phase.