Cold collisions of C2- with Li and Rb atoms in hybrid traps

We present a theoretical investigation of reactive and non-reactive collisions of Li and Rb atoms with C-2(-) molecular anions at low temperatures in the context of sympathetic cooling in hybrid trap experiments. Based on accurate potential energy surfaces for the singlet and triplet states of the Li-C-2(-) and Rb-C-2(-) systems, we show that the associative electronic detachment reaction is inefficient but that it occurs with a large rate for collisions involving excited states of either Li/Rb or C-2(-). We also investigate rotationally inelastic collisions in order to explore the cooling of the translational and rotational degrees of freedom of C-2(-) in hybrid ion-atom traps. The effect of micromotion is taken into account by considering Tsallis distributions of collision energies. We show that the translational cooling occurs much more rapidly than rotational cooling and that the presence of excited atoms leads to losses of anions on a timescale comparable to that of rotational cooling.