Tunable inelastic collisions between magnetically trapped hydroxyl radicals (OH)

We experimentally study collisional properties of cold polar hydroxyl (OH) molecules, which are directly loaded from a Stark-decelerated beam into a strongly confining permanent magnet trap. The OH molecule is both magnetically and electrically polar, which enables the tuning of inelastic collisions as a function of an applied electric field. Based on the experimental data and detailed simulations of the in-trap evolution we find that the OH two-body loss rate depends not only on the magnitude of the magnetic and electric fields, but also on their relative angles. This provides an important step towards a quantitative understanding of the inelastic collisional property and for further evaporative cooling of the molecular sample.