Decisive role of rotational couplings in the dissociative recombination and superelastic collisions ofH2+with low-energy electrons

Abstract

The multichannel quantum-defect theory is used to investigate the role of the numerous couplings between rovibrational states in the dissociative recombination and superelastic collisions of $\text{H}_{2}{}^{+}$ with low-energy electrons, within different molecular electronic symmetries. All the paths accessible are considered. In the case of the singlet gerade symmetry of the neutral system, for example, not only the dominant path, ${^{1}\ensuremath{\Sigma}}_{g}^{+}$, is taken into account, but also ${^{1}\ensuremath{\Pi}}_{g}^{+}$, rotationally coupled to ${^{1}\ensuremath{\Sigma}}_{g}^{+}$, via a frame transformation from the interaction region to the external one. The initial vibrational states investigated are ${v}_{i}^{+}=0--4$. The final rate coefficients are obtained as weighted sums including the so-called ortho-para effect, at room temperature, over all the relevant rotational initial states ${N}_{i}^{+}$, which vary from 0 to 12. The results show that the consideration of rotational effects give a much better overall agreement of the dissociative recombination rate coefficients with experiment, and that, for superelastic collisions, these effects can be used to account, at least partly, for the discrepancies between our former calculations and experiment, which showed a strong vibrational relaxation of $\text{H}_{2}{}^{+}$.