Experimental evidence for an angular dependence in the ionization probability of silver by 1-MeV protons

The K-shell ionization probability for silver has been measured at large angles up to 110degree. A large increase has been found for the smallest impact parameters which can be explained by a dependence on the scattering angle calculated some years ago by Ciocchetti and Molinari. These theoretical results have been introduced in the binary-encounter approximation (BEA) as an additional correction together with the well-known relativistic, trajectory and binding corrections. In the range of impact parameter considered here, the agreement of this fully corrected BEA with the experimental data is satisfying. New results of the ionization probability for 2-MeV protons on Cu are given; as expected from the theory, the ionization probability does not depend on the scattering angle in this particular case