Dissociation dynamics of oriented DF-HF and HF-DF complexes: Evidence for direct and indirect dissociation

Photofragment angular distributions have been obtained for HF-DF and DF-HF, resulting from excitation of the H-F stretching vibrations. The hybrid band associated with this vibration in HF-DF allows us access to both the K-a = 1 <-- 0 and K-a = 0 <-- 0 subbands, while for DF-HF only the K-a = 0 <-- 0 transitions are observed. Analysis of these data provides us with detailed information on the final state distribution of the two rotor fragments, including the intermolecular scalar correlations. The dissociation energies (D-0) are determined for both isomers, namely, 1157(2) cm(-1) and 1082(2) cm(-1) for HF-DF and DF-HF, respectively. The final state distribution for DF-HF shows that the proton donor molecule gives rise to a highly rotationally excited fragment, while the cofragment arising from the proton acceptor is formed in low-j states, a behavior which is consistent with direct dissociation. For HF-DF the results suggest that dissociation is indirect, in the sense that energy is coupled to states involving the closed DF(upsilon=1) channel prior to dissociation.