Toward internal cooling of trapped molecular ions using a spin-orbit split ground state

Preparation of state-selected trapped molecular ensembles is a promising starting point for precision measurements on trapped molecular samples. Translational cooling of trapped molecular ions can be accomplished sympathetically by laser cooling a co-trapped atomic species. To date, in situ cooling of rotational degrees of freedom has been demonstrated only for polar hydrides, by optical pumping into an excited vibrational level. ~However, with increasing reduced mass, the time for vibrational relaxation within the ground state increases, making this scheme problematic for heavy species. We introduce a new cooling scheme, exploiting the diagonal Franck-Condon factors present for molecular ions with spin-orbit split ground states, applicable to certain heavy as well as non-polar species. Progress towards the experimental realization of this scheme for cooling IF{\$}\^{}+{\$}, including the molecular ion production technique, details of the state-preparation, and the proposed state-resolved detection scheme will be discussed.