Ionization and excitation in collisions between antiprotons and H($1s$) atoms

Coupled-state cross sections have been determined for ionization and excitation to states up to H($3d$) in collisions between 1 keV to 16 MeV antiprotons and H($1s$) atoms\footnote {T. G. Winter, Phys. Rev. A (in press).} using the same two-center, as well as one-center, Sturmian bases as for proton projectiles.\footnote{T. G. Winter, Phys. Rev. A {\bf 80}, 032701 (2009).} A detailed comparison and strong contrast at lower energies is made with results for equi-energy proton projectiles, while at high energies all cross sections are tied explicitly to the first-Born limit to better than 1\%. The use of a double-center basis for antiproton projectiles, in spite of there being no capture channels, was first suggested and carried out by Toshima with a large Gaussian basis\footnote {N. Toshima, Phys. Rev. A {\bf 64}, 024701 (2001).}; it provides both additional variational freedom and allowance for antiproton-centered effects, including charge-cloud depletion. Results will be compared with recent theoretical results\footnote{M. McGovern, D. Assafr\~{a}o, J. R. Mohallem, C. T. Whelan, and H. R. J. Walters, Phys. Rev. A {\bf 79}, 042707 (2009).} and earlier results, including experimental ionization cross sections.\footnote{H. Knudsen, U. Mikkelsen, K. Paludan, K. Kirsebom, S. P. M{\o}ller, E. Uggerh{\o}j, J. Slevin, M. Charlton, and E. Morenzoni, Phys. Rev. Lett. {\bf74}, 4627 (1995).}