Towards rotational temperature measurements and controlled dissociation

Molecular ions sympathetically cooled into a Coulomb crystal by laser cooled atomic ions rep- resent in many ways an ideal target for molecular physics studies due to achievable low translational temperatures (∼10 mK) and strong spatial localization (∼1 µm). In particular, in experiments with fo- cused laser beams, both these features can be extremely useful. Here, we present results from experiments on photo-dissociation of MgH + ions in Coulomb crystals, and discuss possible avenues for using such pro- cesses for rotational temperature measurements as well as for manipulating the branching ratio of the dissociation channels Mg+H + and Mg + +H through intensity and frequency control of the laser beams involved.