Cross sections for atomicK-shell ionization by ion impact in the single-particle Glauber approximation

Total cross sections have been computed for $K$-shell ionization in selected multielectron atoms by proton impact using the single-particle Glauber approximation with hydrogenic wave functions. Our single-particle Glauber approximation corresponds to an independent-particle model where explicit coupling with target electrons not directly involved in the interaction is omitted. In principle, the Glauber approximation is valid over a wider region of scattering parameters than is the Born approximation. However, our Glauber results are not in significantly better agreement with observation than simpler Born predictions. For all targets considered at projectile velocities near the peak of the cross section, single-particle Glauber results tend to lie beneath observed cross sections by proton impact, in contrast to previous results for electron impact where, as expected, Glauber results are in better agreement with observations than Born results for low-$Z_2$ targets. Some explanations of the discrepancy and possible extensions of our methods are considered. It is also found that, as the atomic number of the target, $Z_2$, increases, the relative contribution of Glauber corrections to corresponding Born calculations decreases at projectile velocities near and above the peak of the $K$-shell ionization cross section. For $Z_2\gtrsim 5$, the Glauber scattering corrections to Born results for $K$-shell ionization at projectile velocities near and above the peak of the cross section are less than a few percent, e.g., less than errors due to our use of hydrogenic target wave functions. For ${\mathrm{O}}^{+8\mathrm{}}$ + Ne, unlike $p^{+}$ +Ne, significant differences are apparent between Glauber and Born predictions for direct Coulomb ionization.