The reaction of F+D2 at ultra-low temperatures:: the effect of rotational excitation

We report an ab initio study of the dynamics of the reaction F + D-2 --> DF + D, where D-2 is initially in a rotationally excited state (j = 2). The possibility of obtaining ultra-cold molecules and of investigating reaction dynamics at ultra-low temperature relies on the production of molecules in a well defined quantum state and it is important to know the relative efficiency of the rotational quenching and of the chemical reaction. We examine here a reaction with an activation barrier, the reaction of F with D-2, and we find that quenching dominates the reaction when the initial rotational level lies energetically below the barrier, so severe trap loss may occur before the reaction can take place.