Non-q2 scaling of the ionization cross section near the binary peak

Abstract

Cross sections differential in both the ionized electron energy and angle have been calculated using the classical trajectory Monte Carlo method to investigate the binary peak structure in collisions of 1.4 MeV u-1 Uq+ ions with Ar for charge states 11<or=q<or=92. To simulate the effects of the varying screening of the nuclear charge, model potentials have been utilized. At an ejection angle of zero degrees, the magnitude of the binary peak is found to rise at first with increasing projectile charge and then drop. The rise is due to the diminished screening of the projectile nuclear charge with increasing projectile charge state. The drop is ascribed to the influence of the varying screened projectile charge giving rise to a rapidly changing cross section at small angles. In fact, it is found that at 0' the binary peak is 10 times larger for the partially stripped U32+ ion than for the fully stripped U92+ ion.