Direct excitations of He+ and Li++ ions by collisions with protons or antiprotons

The impact parameter formalism of the single-center close-coupling, first-, and second-order Born approximations have been applied to investigate direct excitations of Helium He(2s) and Lithium Li(2s) ions by colliding with protons or antiprotons. The total 3s, 3p, and 3d scaled excitation cross sections are calculated in the scaled impact energy region (2 to 1000 keV). The present work aims to explore the sensitivity of the cross sections to the different electronic transition mechanisms of the considered approaches as well as the charge of each of the projectile and the target nucleus. Also, the calculated cross sections are compared with those obtained by previous theoretical calculations.