Collisional and radiative effects in the state-selective preparation of translationally cold molecular ions in ion traps

We give a detailed characterization of a recently developed method to prepare translationally cold, internally state-selected molecular ions in ion traps [X. Tong, A. H. Winney, and S. Willitsch, Phys. Rev. Lett. 105, 143001 (2010)]. The technique relies on the generation of molecular ions in a well-defined rotational-vibrational quantum state using threshold photoionization followed by sympathetic cooling of the translational motion with laser-cooled Ca+ ions. We discuss the experimental requirements for the successful generation and sympathetic cooling of state-selected ions, explore the influence of collisional and radiative processes on the population redistribution dynamics, and give an assessment of the scope of the method.