Single ionization of helium by antiproton impact

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 eigenstate(s) of He⁺: {1s}, {1s,2s,2p}, and {1s,2s,2p,3s,3p,3d}. 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 (1989); 41, 6359 (1990)] and Hvelplund et al. [J. Phys. B 27, 925 (1994)] 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.