Cold reactive and non-reactive collisions of Li and Rb with C₂^-: implications for hybrid trap experiments

We present a theoretical investigation of cold reactive and non-reactive collisions of Li and Rb atoms with C₂^-. The potential energy surfaces for the singlet and triplet states of the Li--C₂^- and Rb--C₂^- systems have been obtained using the CASSCF/ic-MRCI+Q approach with extended basis sets. The potential energy surfaces are then used to investigate the associative detachment reaction and to calculate rotationally inelastic cross sections by means of the close-coupling method. The effect of the core correlation on the potential energy surfaces is discussed and we estimate the error on the collisional cross sections induced by freezing the 1s orbitals of the carbon atoms. The results are compared to those obtained for the Rb-OH^- system and the applications for hybrid trap experiments are explored. Furthermore, we discuss the possibility to perform Doppler thermometry on the C₂^- anion and investigate the collision process involving excited states. The implications for sympathetic cooling experiments are also discussed.