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 c alculations. This completes our understanding of the various possible decay channels available to superexcited states of HCI and DCI that li e above the first ionization limit. Our experimental and theoretical r esults suggest that the Rydberg states responsible for ion-pair format ion in HCI and DCI via predissociation by the V1SIGMA+ ion-pair state correspond to 1SIGMA+ states that are only weakly autoionized. These s ame Rydberg states appear to act as, at least, one class of precursor states for neutral dissociation to yield excited H and Cl* atoms.