The ionization and excitation cross sections of atomic hydrogen with antiprotons are calculated using the close-coupling method, where the wave function is expanded by atomic states only on protons. The resulting total cross sections are in good convergence and in agreement with other calculations based on the closecoupling method with considerably large basis set. The angular distribution of ionized electrons is calculated by substituting the obtained wave function in the close-coupling method into the integral form of the transition amplitude. Above 100 keV, the angular distributions of ionized electrons are compared for proton-and antiproton impacts.
We have applied close-coupling calculations to calculate the single-ionization cross section of helium by antiproton impact at collision energies above 10 keV. The atomic states of helium are expanded by three sets of eigenstate͑s͒ of He ϩ : ͕1s͖, ͕1s,2s,2p͖, and ͕1s,2s,2p,3s,3p,3d͖. The calculations are in good convergence within these models. The present cross sections are in good agreement with the experimental data of Andersen et al. ͓Phys. Rev. A 40, 7366 ͑1989͒; 41, 6359 ͑1990͔͒ and Hvelplund et al. ͓J. Phys. B 27, 925 ͑1994͔͒ at energies above 40 keV. However, our treatment gives larger cross sections than the data of Hvelplund et al. for lower energies and the disagreement is no less than a factor of 2 near 10 keV.
Abstract. Electron excitation collision strengths for all the transitions among 3s, 3p, 3d, 4s, 4p, 4d, 4f states of the five Na-like ions Al III, Si IV, S VI, Ar VIII and Ca X are calculated in the R-matrix approximation. Eleven target terms are included in the expansion of the total wavefunction. These collision strengths are averaged over a Maxwellian velocity distribution to obtain effective collision strengths as a function of electron temperature. The resulting values are compared with the results of previous less elaborate calculations to find some disagreements.
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