Energy efficiency in surmounting the central energy barrier: a quantum dynamics study of the OH + CH3 → O + CH4 reaction.

The present quantum dynamics study of the OH + CH3 shows that, for this "central" (slightly early) barrier reaction, it is the vibrational energy of the reactant OH that is more effective in promoting the reactivity than the translational energy; while previous studies show that, for its forward reaction O + CH4 also with a "central" (slightly late) barrier, it is the translational energy that is more effective in surmounting the energy barrier than the vibrational energy. Since both barriers deviate only slightly from the center of the potential energy surface, these findings indicate that for these two reactions with more-or-less central barriers, a small change of the barrier location can greatly affect which energy form determines the reaction reactivity. This study also shows that both the rotational excitation states of OH and CH3 hinder the reactivity.