Details and consequences of the nonadiabatic coupling in the Cl(P-2)+H-2 reaction

In an investigation of nonadiabaticity in the Cl+H-2 reaction we examine the various coupling terms responsible. By neglecting various of these terms, we show that the spin - orbit coupling in the Cl atom is primarily responsible for non Born - Oppenheimer effects in this reaction, and that the anisotropies in the contributing electronic potential energy surfaces as well as Coriolis terms, are considerably weaker in their effect. Neglect of all coupling except spin - orbit leads to little change in the calculated reaction probabilities both for the Born - Oppenheimer allowed [Cl(P-2(3/2))+H-2] and Born - Oppenheimer forbidden [Cl(P-2(1/2))+H-2] reactions. This implies that one can safely neglect the coupling between different values of the electronic projection quantum number omega. Consequently, the computational effort involved in an accurate quantum scattering treatment of this (and, hopefully, other similar reactions) can be substantially reduced.