Fragmentation processes of C60 in multiple electron loss and capture collisions of 2-MeV Si2+

An experimental study of ionization and fragmentation of C-60 has been performed for 2-MeV Si2+ incident ions under charge-changing conditions. Time-of-flight (TOF) spectra of product ions and number distributions of secondary electrons (n(e)) were measured in coincidence with charge-selected outgoing projectiles. TOF spectra from transiently formed highly charged C-60(r+) ions are obtained for individual charge states r, and n(e) distributions correlated with size-fixed C-m(+) ions are also obtained for m < 15. It is found that mass spectra and n(e) distributions are both significantly different between loss and capture collisions, whereas a remarkable similarity in the partial n(e) distributions is observed almost independently of the different charge-changing conditions when compared at given C-m(+) ions size. We find also that a number of secondary electrons as high as 20 are emitted in the production of small fragment ions. Furthermore, small fragment ions are produced predominantly in close collisions even at very low charge states of r similar or equal to 3 in comparison with distant collisions. This indicates that the energy partition rate between ionization and internal excitation might be considerably different in close and distant collisions.