ENERGY-LOSS AND CHARGE-EXCHANGE - STATISTICS AND ATOMISTICS

This is a brief summary of recent work by the authors on (I) statistic al aspects of the interplay between charge exchange and electronic ene rgy loss and (II) atomistics of charge-dependent stopping of heavy ion s. (I) A matrix formalism has been developed that specifies energy-los s spectra differential in entrance and exit state. Examples refer to a simple two-state system where experimental results exist. The precise definition of energy loss needs attention when particles change ident ity. (II) The relation between stopping cross section and ion charge h as been studied on the basis of the Bohr theory. A dimensionless param eter has been identified which governs the significance of projectile screening, indicating that the stopping cross section for target excit ation is as sensitive to the target as to the projectile. The contribu tion of projectile excitation to electronic stopping is discussed qual itatively. Comparison with measured fixed-charge stopping cross sectio ns shows good to satisfactory agreement. (C) 1998 Elsevier Science B.V .