Elastic and charge transfer cross sections for low to ultralow $\mathrm{H}(1s)+{\mathrm{H}}^{+}$ collisions. Quantal and semiclassical calculations

The elastic scattering and resonant charge transfer integral cross sections in $\mathrm{H}(1s)+{\mathrm{H}}^{+}$ collisions are computed for the center-of-mass energy range of ${10}^{-10}-10$ eV. Fully quantal and semiclassical approaches are utilized in these calculations. The reliability of the semiclassical approximation for very low collision energies is discussed. The results are compared with available data from the literature.