CHARGE-EXCHANGE AND ENERGY-LOSS STATISTICS OF SWIFT PENETRATING IONS

A general and powerful formalism has been developed for computation of energy-loss spectra of penetrating charged particles in the presence of charge exchange. Options on the input side are the cross sections f or electron capture and loss, transition rates for radiative and nonra diative spontaneous processes and their associated energy losses or ga ins, and finally, cross sections for all processes that contribute to particle stopping but are not associated with charge exchange. The for malism generates an n x n transfer matrix, where n is the number of st ates needed for an adequate description of the projectile under consid eration. This matrix delivers the joint distribution of energy loss an d exit charge state for a given incident charge state and energy. The formalism can be used in principle as an alternative for Monte Carlo s imulation, but until now we have concentrated on direct evaluation of key experimental parameters related to the energy-loss spectrum integr ated over all exit charge states, in particular, mean energy loss, str aggling, and skewness. Generally, valid analytic expressions have been found for these quantities, each of which can be separated into a sta tionary term representing charge state equilibrium and a transient dep ending on the incident charge state. A brief survey is given of curren t analytic and numerical efforts addressing other experimental paramet ers.