Charge transfer in high velocity Cn++He collisions

Dissociative and non-dissociative charge transfer cross sections in high velocity (v = 2.6 au) collisions between ionic carbon clusters C-n(+) (n = 2-10) and helium atoms have been measured. The sum of the cross sections has been found to increase significantly with n. Measurements of branching ratios for all fragmentation channels of excited C-n clusters are reported. The summed branching ratios associated with a given number of emitted fragments exhibit odd-even alternations reflecting the higher stability of the species having an odd number of atoms. From an analysis of the summed branching ratios within the statistical microcanonical metropolis Monte Carlo model, and knowing the temperature of the incident clusters, deposited energy distributions due to the charge transfer process are deduced (n = 5-9). These distributions, of similar characteristics whatever n, peak around 4-5 eV and exhibit a large percentage of superexcited states situated above the continuum.