Fragment ion distribution in charge-changing collisions of 2-MeV Si ions with C-60 - art. no. 032702

We have measured positive fragment ions produced in collisions of 2 MeV Siq + (q = 0, 1, 2, 4) projectiles with a C-60 molecular target. The measuremen t was performed with a time-of-flight coincidence method between fragment i ons and charge-selected outgoing projectiles. For all the charge-changing c ollisions investigated here, the mass distribution of small fragment ions C -n(+) (n=1-12) can be approximated fairly well by a power-law form of n(-la mbda) as a function of the cluster size n. The power lambda derived from ea ch mass distribution is found to change strongly according to different cha rge-changing collisions. As a remarkable experimental finding the values of lambda (loss) in electron loss collisions are almost the same for the same final charge states k irrespective of the initial charge q, exhibiting a n early perfect linear relationship with k. We also performed calculations of the projectile ionization on the basis of the semiclassical approximation and obtained inelastic energy deposition for individual collision processes . The estimated energy deposition is found to have a simple correlation wit h the experimentally determined values of lambda (loss).