Dissociation dynamics of mass-asymmetric molecules in impact on solid surfaces

The dissociation of heteronuclear molecules, induced by high-energy collisions with chemically inert surfaces, is studied by classical trajectories. Results for IBr and ICl in collisions with an MgO surface are compared with previous calculations for I₂. New qualitative effects are found in the case of ICl due to the high mass asymmetry, shown in the energy dependence of the dissociation probability, and in the velocity and the angular distribution of the dissociation fragments. The new features (compared with I₂) are interpreted in terms of two different possible pathways for dissociation, corresponding respectively to collisions where the light or the heavy atom strikes the surface first. The results provide considerable insight into the role of collider masses in the dynamics of dissociation upon impact on surfaces.