A series of computations based on multichannel quantum defect theory have been performed in order to produce the cross sections of rotational transitions (excitationsto 10) and of their competitive process, the dissociative recombination, induced by collisions of HD + ions with electrons in the energy range 10 −5 to 0.3 eV. Maxwell anisotropic rate coefficients, obtained from these cross sections in the conditions of the Heidelberg Test Storage Ring (TSR) experiments (k B T t = 2.8 meV and k B T l = 45 μeV), have been reported for those processes in the same electronic energy range. Maxwell isotropic rate coefficients have been presented as well for electronic temperatures up to a few hundred Kelvins. Very good overall agreement is found between our results for rotational transitions and the former theoretical computations as well as with experiment. Furthermore, due to the full rotational computations performed, the accuracy of the resulting dissociative recombination cross sections is improved considerably.

We report calculations of H 2 − states using a variational R-matrix approach combined with multichannel quantum defect theory. Several Rydberg series converging to the 2pπ state of the H + 2 ion core are established and their mutual channel interactions characterized. The influence of the external electron on the chemical bond is found to be particularly strong in these electronically and chemically weakly bound states.

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Abstract. Recent advances in the stepwise multichannel quantum defect theory approach of electron/molecular cation reactive collisions have been applied to perform computations of cross sections and rate coefficients for dissociative recombination and electron-impact rovibrational transitions of H + 2 , BeH + and their deuterated isotopomers. At very low energy, rovibronic interactions play a significant role in the dynamics, whereas at high energy, the dissociative excitation strongly competes with all other reactive processes.a Corresponding author: Ioan.Schneider@univ-lehavre.fr This is an Open Access article distributed under the terms of the Creative Commons Attribution License 4.0, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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Abstract. We report R-matrix calculations of doubly-excited 3 − g states of molecular hydrogen corresponding to 3d n˜ configurations. These states form Rydberg series converging to the 3d series limit. They lie in the continuum of the doubly-excited states of 3 − g symmetry built on the 2p ion core, and therefore they are autoionized. Calculations of resonance positions and widths are presented.

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