Scattering of protons and antiprotons by hydrogen-like atoms

The impact parameter method is applied to the excitation of hydrogen-like atoms in the 2s-state. Cross-sections for the n=3 excitation of H(2s) atoms and H+(2s), Li+(2s) ions, by colliding with protons ((p) over bar) and antiprotons are evaluated for incident energies, ranging from 1.5 KeV to 2500 KeV. The results of calculations for hydrogen atoms are compared with a previous work.