The mobility of ground-state Gd+ ions in He and Ar gases is addressed theoretically to bridge the surprising gap between the experimental and previous theoretical data. An accurate ab initio coupled cluster approach is used to compute scalar-relativistic interaction potentials for all the molecular states of the Gd+-He and Gd+-Ar pairs. Then a multireference configuration interaction method is used to account for the spin-orbit coupling between the states. This greatly improves the theoretical mobility values at low fields for the 156Gd+(4f75d6s 10Do 5/2) ion, bringing them in close agreement with the room-temperature measurements. Several approximations to transport cross sections for the multistate open-shell collisions are assessed and discussed. Accurate description of the transport properties of the heavy open-shell ions is shown to require a demanding high-level ab initio approach. Temperature- or field-dependent mobility data are needed for a more in-depth assessment of the ab initio interaction potentials and dynamic approximations to the cross sections for open-shell ions.
- Ab initio interaction potentials
- Gadolinium ion
- Gas-phase ion mobility