Excitation of Sn K- and L- and Ta L-shell x rays by 1.4-4.4-MeV protons

Excitation functions and absolute cross sections for Sn K- and L-shell and Ta L-shell x-ray production by proton impact have been measured over the energy range 1.4-4.4 MeV with a Si(Li) detector. The results, combined with our measurements on other elements, are compared with existing theories. In the calculation of ionization cross sections from the plane-wave Born approximation, we discuss the effect of a relativistic correction for the ionization potential. The plane-wave Born approximation with the correction due to the Coulomb deflection gives the best fit for Sn K x-ray production and the binary-encounter approximation is the best for Sn L and Ta L x-ray production. The semiclassical approximation based on the impact-parameter treatment predicts values which are not in agreement with the data on Sn L x rays. The scaled universal excitation curve based on the binary-encounter approximation gives good fits to K-shell ionizations but seems to show some disagreement for L-shell ionizations. The dependence of the K K ratio of Sn on the target thickness was investigated but it was found that the ratio is constant within the experimental uncertainty. Relative intensities for the transitions L , L , L, and Ll are also compared with the theories.