Rotational effects in dissociative recombination: theoretical study of resonant mechanisms and comparison with ion storage ring experiments

The cross section for dissociative recombination of ions is calculated in the energy range 1 meV - 13 eV, using an extended MQDT approach which includes simultaneously electronic, vibrational and rotational interactions. We analyse the effect of rotation on the low-energy resonance structure due to interfering bound Rydberg states, whereas at higher energy, above the ion dissociation limit, competition with dissociative excitation is introduced. The absolute cross section measured in the ion storage ring CRYRING is well reproduced in shape and size below 0.3 eV if the theoretical results are averaged with a 300 K Boltzmann distribution of ion rotational levels, in equilibrium with the beam tube at room temperature. Beyond this energy and up to the ion dissociation threshold (2.7 eV), the experimentally measured cross section is considerably larger than the theoretical one, although similarities in shape are still present. Above the dissociation limit, we obtain an overall good agreement between theory and experiment.