Variations of Projectile Effective Charge in Analyses of Stopping Powers for Heavy Ions

The most recent version of modified Bethe-Bloch stopping power theory has been applied to several different sets of heavy ion stopping power measurements to establish an adequate effective charge parametrization. Two such parameters proved sufficient to provide satisfactory fits for all but one set of measurements. Separate approaches to inclusion of the Barkas effect, depending on whether or not provision must be made for close collision contributions to the Barkas-effect term, yielded results incapable of discerning an unequivocal choice between the two alternatives. A suggestion of structure in the dependence of each charge state parameter on projectile atomic number emerged from the analysis.