Inner shell ionization of intermediate- and high-Z elements produced by collisions with fast heavy charged particles

A review of the theoretical approaches to inner-shell ionization in fast ion-atom collisions is presented. K x-ray yields have been measured for ten elements ranging from Fe (Z = 26) to Au (Z = 79) using 30 to 100 MeV alpha particles and for Fe, Cu and Sn using 28.2 to 196.4 MeV carbon ions. The ''smoothed'' cross sections were used in comparisons with the predictions of the binary encounter approximation (BEA), the plane wave Born approximation (PWBA) and the binding corrected PWBA calculations and resulted in the observation of a systematic atomic-number dependent deviation between experiment and theory. By comparing the measured cross sections to the universal BEA curve at velocity ratios in which the mean electron velocity was calculated ''semi''-relativistically, overall agreement within +-16 percent was obtained for all elements studied. The theoretically predicted z2-dependence of the PWBA and BEA was tested by measuring the x-ray yield ratio of Cu using identical velocity alpha particles and deuterons and alpha particles and carbon ions. Cross sections for the ionization of the L-shell in seven elements ranging from Sn (Z = 50) to Pb (Z = 82) and for the L-subshells of Tb, Tm, Au and Pb were measured using 30 to 80 MeV alpha particles. Subshell ionization cross sections were deduced from the Lα and Lγ x-ray lines and were compared to the predictions of the BEA, PWBA and the SCA. A computer program (ORION), written to compute theoretical cross sections based on the BEA, PWBA and the SCA, and to calculate the average depth of x-ray production and emission for a given target thickness and incident projectile, is also described