First-order theories for adiabatic L-shell ionization by protons.

Abstract

[ital L]-shell ionization cross sections, evaluated as mean values of the experimental data, were compared with the first-order theoretical values obtained by the plane-wave Born and semiclassical method. Hydrogenic Dirac wave functions in the united-atom limit were employed in the calculation. The plane-wave Born approximation cross sections with Dirac-Hartree-Slater wave functions were obtained from the tables of Chen and Crasemann [At. Data Nucl. Data Tables 33, 217 (1985); 41, 257 (1989)]. The agreement between the experimental and semiclassical cross sections was generally better than 20%, except for the [ital L][sub 1] subshell of heavy elements and for the very adiabatic region of [ital L][sub 2,3] subshells. The differences between both sets of data were largely reproduced by a simplified coupled-channel calculation performed nonrelativistically for a single final state. The calculation also suggests that, due to the uncertainties of the fluorescence yields, the ionization cross sections deduced from the measured data are overestimated by 10%.