title: Rotationally inelastic collisions of H2+ions with He buffer gas: Computing cross sections and rates.
abstract: We present quantum calculations for the inelastic collisions between H2+molecules, in rotationally excited internal states, and He atoms. This work is motivated by the possibility of experiments in which the molecular ions are stored and translationally cooled in an ion trap and a He buffer gas is added for deactivation of the internal rotational population, in particular at low (cryogenic) translational temperatures. We carry out an accurate representation of the forces at play from an ab initio description of the relevant potential energy surface, with the molecular ion in its ground vibrational state, and obtain the cross sections for state-changing rotationally inelastic collisions by solving the coupled channel quantum scattering equations. The presence of hyperfine and fine structure effects in both ortho- and para-H2+molecules is investigated and compared to the results where such a contribution is disregarded. An analysis of possible propensity rules that may predict the relative probabilities of inelastic events involving rotational state-changing is also carried out, together with the corresponding elastic cross sections from several initial rotational states. Temperature-dependent rotationally inelastic rates are then computed and discussed in terms of relative state-changing collisional efficiency under trap conditions. The results provide the essential input data for modeling different aspects of the experimental setups which can finally produce internally cold molecular ions interacting with a buffer gas.
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors.forename: Mario
authors.identifier: 0000000175946501
authors.initials: M
authors.lastname: Hernández Vera
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors.forename: F A
authors.identifier: 0000000280439042
authors.initials: FA
authors.lastname: Gianturco
authors.affiliation: Institut für Ionenphysik und Angewandte Physik, Universität Innsbruck, Technikerstr. 25/3, A-6020 Innsbruck, Austria.
authors.forename: R
authors.identifier: 0000000179356066
authors.initials: R
authors.lastname: Wester
authors.affiliation: Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Paris-Saclay, Université Paris-Saclay, Orsay, France.
authors.forename: H
authors.initials: H
authors.lastname: da Silva
authors.affiliation: Laboratoire Aimé Cotton, CNRS, Université Paris-Sud, ENS Paris-Saclay, Université Paris-Saclay, Orsay, France.
authors.forename: O
authors.identifier: 0000000194983754
authors.initials: O
authors.lastname: Dulieu
authors.affiliation: Institut für Experimentalphysik, Heinrich-Heine-Universität Düsseldorf, Universtätsstr. 1, D-40225 Düsseldorf, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Schiller