Bethe cross sections for the sodium isoelectronic sequence

Bethe cross sections for the excitation of Na-like ions to the 3 2P/sub 1/2/, 3 2P/sub 3/2/, 4 2P/sub 1/2/, and 4 2P/sub 3/2/ states from the ground state are computed from the relativistic Hartree-Fock wave functions. As the nuclear charge is increased, excitation cross sections to the 2P/sub 3/2/ states are affected far more by relativistic effects than those to the 2P/sub 1/2/ states. The asymptotic ionization cross sections for the neutral Na atom and Fe15+ ion are computed from a sum rule, i.e., by subtracting the sum of discrete excitation cross sections from the total inelastic-scattering cross section obtained from the sum rule. The ionization cross sections thus obtained are sigma/sub ion/(Na) = β-2(2.51]ln[β2/(1-β2)] - β2] + 26.3) x 10-20 cm2, sigma/sub ion/(Fe15+) = β-2(0.209 ]ln[β2/(1-β2)] - β2] + 1.64) x 10-20 cm2, where β is the incident electron or proton speed divided by that of light. The cross section for Na is in agreement with that calculated by McGuire, but not with the electron-impact experiment by McFarland and Kinney. The ionization cross section for Fe15+ is a factor of 2 to 3 larger than the Coulomb-Born results by Rudge and Schwartz and by Bely in the asymptotic region