Impact Excitations of Hydrogen Atoms in Collisions with Protons and Antiprotons

The direct impact excitations of ground-state hydrogen atoms by protons and antiprotons are investigated by using an impact parameter treatment. The calculations are performed within the solution of the coupled differential equations arising from the one-center atomic-orbital close-coupling approach as well as the impact parameter version of the first and second Born approximations. We have considered calculations that allow couplings to the n=1–5 states (up to g sub-levels) of the target atom as well as others, which neglect the effect of all states other than the initial and final states of the target atom. The sensitivity of the cross sections to the charge of the projectile is studied. The calculated cross sections are compared with those obtained by previous theoretical and experimental results.