Production of Lyman-$alpha$ radiation in collisions of protons and hydrogen atoms

The cross sections for Lyman-$\ensuremath{\alpha}$ production by the processes ${\mathrm{H}}^{+} (or {\mathrm{D}}^{+})+\mathrm{H}(1S)\ensuremath{\rightarrow}{\mathrm{H}}^{+} (or {\mathrm{D}}^{+})+\mathrm{H}(2P)$ (direct excitation) and ${\mathrm{H}}^{+} (or {\mathrm{D}}^{+})+\mathrm{H}(1S)\ensuremath{\rightarrow}\mathrm{H}(2P) [\mathrm{or}\mathrm{D}(2P)]+{\mathrm{H}}^{+}$ (charge transfer) have been measured over the energy range 0.75-29 keV using a modulated cross-beam technique with liquid-helium cryopumping. Signals from the direct excitation and the charge transfer were separated by a Doppler-shift technique. The absolute cross sections were assigned by comparison with excitation of Lyman-$\ensuremath{\alpha}$ on electron impact. For direct excitation, general agreement in shape with the data of Stebbings et al. and of Morgan, Geddes, and Gilbody was found except for structure at 1.3 keV. The pseudostate calculations of Cheshire, Gallaher, and Taylor predicted the present experimental points well. For charge transfer, our results agree with those of Morgan, Geddes, and Gilbody at energies higher than 11 keV and have similarity in shape to the work of Stebbings et al. A peak appeared in our cross-section curve at the energies around 1.7 keV. Acceptable agreement with the pseudostate calculations was found up to the maximum energy except for the appearance of the peak at 1.7 keV.