Photodissociation spectroscopy of OH+ molecular ions at the TSR storage ring

When infrared active molecular ions are stored in a heavy-ion storage ring, a fast beam of vibrationally and rotationally relaxed molecules can be obt ained. This opens up new opportunities for various experimental studies in molecular ion physics, particularly those involved with spectroscopy and di ssociation dynamics of excited states. The analysis of such experiments is facilitated by the fact that the information on the initial states is able to identify and, therefore, eliminate them from the assignment problem. Mor eover, when the intensity of the measured transitions is monitored as a fun ction of storage time, the dependence of these processes on the degree of i nternal relaxation is revealed. We demonstrate these general principles by application to near-threshold dissociation spectroscopy of the OH+ molecula r ion. The structure of quasibound levels near the dissociation limit of OH + and its dissociation energy are deduced.