The probability of electron capture at fixed scattering angles in H+-H collisions

Abstract

The wave treatment of electron capture is used in calculations of differential cross sections for H+-H collisions at different scattering angles and at energies between 100 eV and 2 keV. It is shown that the impact parameter treatment is inaccurate for calculations of differential capture cross sections except at high energies and large scattering angles, that is above about 5 keV when the scattering angle of the incident proton is 0.5° and above about 0.5 keV when the scattering angle is 5°. At small angles and energies the two-state wave approximation shows considerable damping of the oscillations in the probability of electron capture, in qualitative agreement with experiment. The damping due to this wave effect is compared with that due to 2pσu - 2pπu coupling (based on calculations made by Bates and Williams in 1964), and it is shown that the wave effect causes more damping especially at low energies. The two-state wave treatment is corrected for 2pσu - 2pπu coupling in the case of 3° scattering and compared with the experimental results of Lockwood and Everhart obtained in 1962. Closer agreement with experiment is obtained than hitherto. The effect of rainbow scattering, important at low energies and for small scattering angles, is also discussed.