ION-PAIR FORMATION IN THE PHOTODISSOCIATION OF HCL AND DCL

The vibrationally resolved excitation functions for Cl- formation from jet-cooled HCl and DCl, following photoabsorption in the region 75-86 nm (HCl/DCl+hv.H+/D++Cl-), are reported and compared with ab initio calculations. This completes our understanding of the various possible decay channels available to superexcited states of HCI and DCI that lie above the first ionization limit. Our experimental and theoretical results suggest that the Rydberg states responsible for ion-pair formation in HCI and DCI via predissociation by the V1SIGMA+ ion-pair state correspond to 1SIGMA+ states that are only weakly autoionized. These same Rydberg states appear to act as, at least, one class of precursor states for neutral dissociation to yield excited H* and Cl* atoms.