nS1and nP1excitations of heliumlike ions by electrons: A precise distorted-wave polarized-orbital approach

Total-cross-section results for excitations of n ${\mathrm{}}^1$S and n ${\mathrm{}}^1$P (n=2–6) states of several heliumlike ions from the 1 ${}_{}{}^1{}_{}{}^{}S$ ground state are reported in this paper for energies near threshold to above 5 times the threshold energy. These results are obtained using a reliable distorted-wave polarized-orbital approach where distortions are included due to static, polarization, and exchange effects appropriately as desired in both the initial and final channels of the distorted waves. Sensitivity of the results with respect to different choices of ion-target wave functions (such as hydrogenic, Hartree-Fock, and configuration-interaction types) in the present model is also examined. The results are compared with other available theoretical estimates.