Rainbow structure and g–u-interference effects in the elastic scattering of low energy protons on deuterium and hydrogen atoms

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Abstract
Elastic differential cross sections for the scattering of low energy protons (Ec.m.=11–142 eV) on H and D atoms have been obtained. The curves exhibit clearly rainbow structure, g–u oscillations and a type of rapid interference, if coherent scattering of both σg and σu potential curves is taken into account. For comparison, partial wave calculations have been performed using WKB phases and a two‐state (1sσg, 2pσu) approximation. The agreement with both experimental results and three‐state (1sσg, 2pσu, 2pπu) calculations of Knudson et al. is excellent, which implies that rotational coupling between the 2pσu and 2pπu potential curves can be neglected. It is shown that the reduced phases a=√E/2μN can be described as a single function of the reduced angle τ=Eϑ for all energies and both isotopes. This function agrees with both two‐state calculations of the authors and three‐state calculations of Knudson et al.