DYNAMICS OF COMPETING CHANNELS IN THE S-/H2 COLLISIONAL SYSTEM

A dynamical study of the various channels competing in the S-/H2 collisional system has been performed in a crossed beam experiment with multicoincidence detection of two products. Energy range extends from the threshold of reactions to 20 eV. Different dynamical behaviours are observed as a function of collisional energy for reactive detachment and simple detachment channels. Part of them were already observed in halide ion-H2 systems and interpreted in term of adiabatic or diabatic behaviour at the crossing seam between two ionic surfaces. This seam is the locus where the active electron changes core. In the S-/H2 system, the number of surfaces is greater than in the halide ion-H2 systems. The main originality lies in the existence of a well in the ground state continuum corresponding to the formation of SH2 molecule. An attempt to explain the mechanism of associative detachment is given. The dissociation of the H2S molecule is observed at threshold. The SH product is sideway scattered at 90°, this behaviour should reflect a large rotational excitation of the molecule. © 1990.