Reactive and detachment processes in halide ion-H 2 collisions

Abstract

A systematic investigation of the competition between reactive and detachment channels in halide ions-H 2 collisions has been undertaken using a multicoincidence technique. Contour maps for detaching and non-detaching processes are obtained. It is found that the F −-H 2 system behaves differently from that involving the heavier halide ions. The competition between reaction and reactive detachment processes for all systems is well accounted for by considering a non-adiabatic interaction between the two lowest ionic potential surfaces as previously discussed. From a kinematic point of view, this study suggests that at low energy (< 12 eV), the various F −-H 2 processes proceed via a scattering on the H 2 molecule as a whole, in contrast with Cl −-H 2, Br −H 2 and I −-H 2 cases for which a hard scattering on only one H atom is the dominant step. This special feature leads to a simple expression for the “isotopic effect” in total cross sections of Cl −-H 2, Cl −-HD and Cl − -D 2 collision which fits well the large effect observed by Huq et al.