SWIFT CLUSTER-ATOM COLLISIONS - EXPERIMENT AND MODEL-CALCULATIONS

Single, double and triple ionization cross sections of 10 MeV C-5(+) p rojectiles colliding with He atoms have been measured. This was achiev ed thanks to a new experimental set-up allowing for a complete collect ion and unambiguous identification (in particular with respect to thei r charge) of all the fragments emitted by the dissociative C-5(Q+) spe cies (Q = 2, 3, 4). As a first attempt to understand the mechanisms of ionization in the cluster we use these results, together with those w e obtained in the identical velocity 2 MeV C+ --> He system, for testi ng the predictions of an {independent atoms}-atom collision calculatio n within the impact parameter formalism and using the independent-elec tron approximation. The model is found to be surprisingly good in pred icting the cluster-atom results when appropriate (i.e. able to reprodu ce the atom-atom case) impact parameter dependent ionization probabili ties are used.