The vibrational dependence of dissociative recombination: Cross sections for ${\rm N}_2^ +$N2+

Abstract

Theoretical ab initio calculations are reported of the cross sections for dissociative recombination of the lowest four excited vibrational levels of N2(+) at electron energies from 0.001 to 1.0 eV. Rydberg vibrational levels contributing to the cross section structures are identified as are dissociative channels contributing more than 10(-16) cm(2) to the total cross sections. In contrast to the prior study of v = 0 (S. L. Guberman, J. Chem. Phys. 137, 074309 (2012)), which showed 2(3)Πu to be the dominant dissociative channel, 4(3)Πu is dominant for v = 1. Both 2 and 4(3)Πu are major routes for dissociative recombination from v = 2-4. Other routes including 2(3)Σu(+), 3(3)Πu, 2(1)Πu, 2(3)Πg, 2(1)Σg(+), 1(1)Δg, and b('1)Σu(+) are significant in narrow energy ranges. The results show that minor dissociative routes, included here for N2(+), must be included in theoretical studies of other molecular ions (including the simplest ions H2(+) and H3(+)) if cross section agreement is to be found with future high resolution dissociative recombination experiments. The calculated predissociation lifetimes of the Rydberg resonances are used in a detailed comparison to two prior storage ring experiments in order to determine if the prior assumption of isotropic atomic angular distributions at "zero" electron energy is justified. The prior experimental assumption of comparable cross sections for v = 0-3 is shown to be the case at "zero" but not at nonzero electron energies. Circumstances are identified in which indirect recombination may be visualized as a firefly effect.