The effect of a conical intersection on cross sections for collision-induced dissociation

The cross section for H+H2(v, j)→3H, where v and j denote selected vibrational and rotational quantum numbers, is calculated by the quasiclassical trajectory method, using trajectory surface hopping to include the effect of the first excited electronic state which has a conical intersection with the ground state. The excited electronic state allows for collision-induced dissociation by the process H+H2(X 1Σ+g)→H3(1 2A′)→H3(2 2!iA′) →H +H2(b 3Σ+u) →3H, where the various transitions all occur in the course of a single collision. This new surface hopping mechanism increases the cross sections and rate constants for production of unbound states by 2%–44% for the conditions examined.