N2+(2Σg) and Rb(2S) in a hybrid trap: modeling ion losses from radiative association paths

10 pags., 8 figs., 2 tabs. -- Open Access funded by Creative Commons Atribution Licence 3.0
By employing ab initio computed intermolecular potential energy surfaces we calculate the radiative association probabilities and rates for two different associative mechanisms involving trapped molecular ions N2 +(2Sg) interacting either directly with ultracold Rb atoms or undergoing charge-exchange (CE) processes leading to the formation of complexes of the strongly exothermic products N2(X1Sg) plus Rb+(1S0). The two processes are expected to provide possible paths to ion losses in the trap within the timescale of experiments. The present calculations suggest that the associative rates for the ‘vibrational’ direct process are too small to be of any significant importance at the millikelvin temperatures considered in the experiments, while the ‘vibronic’ path into radiatively associating the CE products has a probability of occurring which is several orders of magnitude larger. However the reaction rate constants attributed to non-adiabatic CE [F. H. J. Hall and S. Willist, Phys. Rev. Lett., 2012, 109, 233202] are in turn several orders of magnitude larger than the radiative ones calculated here, thereby making the primary experimental process substantially unaffected by the radiative losses channel.
The participating groups in Innsbruck and Basel gratefully acknowledge the Marie-Curie Initial Training Network ‘‘COMIQ: Cold Molecular Ions at the Quantum limit’’ for providing financial support for the present collaboration when this work was started. TGL and PV acknowledge MICINN Grants no. FIS2014-51993-P and FIS2017-83157-P. SW acknowledges support from the Swiss National Science Foundation under grant no. 200020-175533.
We acknowledge support of the publication fee by the CSIC Open Access Support Initiative through its Unit of Information Resources for Research (URICI)