Ionization and excitation in collisions between antiprotons and H(1s) atoms studied with Sturmian bases

Abstract

Coupled two-center as well as one-center Sturmian cross sections have been determined for ionization and excitation in $\mathrm{p\ifmmode \bar{}\else \={}\fi{}}$-H($1s$) collisions at $\mathrm{p\ifmmode \bar{}\else \={}\fi{}}$ energies from 1 to 16 000 keV, following the author's recent work for $p$-H($1s$) collisions [Phys. Rev. A 80, 032701 (2009)]. Basis convergence is studied in detail. Results for ionization and excitation are compared to other coupled-state results and to numerical results, as well as limited experimental results for ionization only. Except for the large, two-center coupled-Gaussian-pseudostate calculation of Toshima for ionization only [Phys. Rev. A 64, 024701 (2001)], previous calculations employed one-center bases, including a one-center Sturmian calculation by Igarashi et al. [Phys. Rev. A 61, 062712 (2000)]. A strong contrast with $p$-H collisions is confirmed at intermediate energies, while at high energies the extent of agreement is revealed between coupled-state results for the two collisional systems, as well as with first Born results.