Absolute excited-state populations of fast carbon ions in solids

The absolute populations of C5+ ions emerging in excited states from carbon foil targets of thicknesses ranging from 10 to 125 atoms.AA2 have been determined for incident beams of 24, 35 and 43 MeV C4+. For a given beam energy the population of 5+ ions emerging in the 2p state was found to follow the total 5+ charge fraction as the foil thickness was increased, suggesting that the cross section for excitation of ground-state electrons was larger than the cross section for electron capture by the bare nucleus. The authors found that in the cases studied, the 2p population formed (17+or-5)% of the total 5+ charge fraction. Populations for other excited states are also reported. The results are consistent with the size of the density effect previously observed in projectile charge-state distributions for the same collision system.