A new collision chamber design has made possible differential measurements of scattering of protons on atomic hydrogen target atoms. The scattering takes place in the interior of a furnace where hydrogen gas is dissociated. Electron capture probability is measured vs proton energy for protons passing nearly through the center of isolated hydrogen atoms such that the incident particle is scattered through an angle of 3°. This shows a resonant structure with maxima at energies of 0.78, 1.57, 3.92, and 20.1 kev. A simple model is presented for looking at these resonances. In the light of this model and previous theoretical work, the location of the high-energy maximum is unexpectedly low, and this suggests that a phase constant is needed to achieve agreement between experiment and theory. The ${\mathrm{H}}^{+}$ on H data presented here are compared with those for the other combinations, ${\mathrm{H}}^{+}$ on ${\mathrm{H}}_2$, ${\mathrm{H}}^{+}$ on He, and ${\mathrm{He}}^{+}$ on He, which also show resonant electron capture.

• Received 21 August 1961

DOI:https://doi.org/10.1103/PhysRev.125.567