Mutual neutralization in H+ + H- collisions: An improved theoretical model

The total and differential cross sections of mutual neutralization in H+ + H- collisions are calculated ab initio and fully quantum mechanically for energies between 0.001 and 600 eV. Effects which have not previously been considered in studies on mutual neutralization (MN) for this system, such as inclusion of rotational couplings and autoionization, are investigated. Adiabatic potential curves corresponding to the relevant states of 1Eg+, 1Eu+,1 pi g and1 pi u symmetries as well as radial and rotational nonadiabatic couplings are computed ab initio. A quasidiabatic model is developed and applied in order to investigate the importance of higher excited states as well as the inclusion of autoionization. Molecular data for the lowest electronic resonant state in each symmetry are obtained by performing electron scattering calculations. It is shown that rotational couplings cause a significant increase of the total MN cross section while autoionization plays a minor role as a loss mechanism. Additionally, a differential cross section is obtained that is symmetric around 0 = 90 degrees. This result is in disagreement with a previous theoretical calculation where it was found that the differential cross section is dominated by backwards scattering.