Theoretical study of the breakdown of the Born–Oppenheimer approximation in the Cl(2 P ) + D2 ( v = 0, j = 0 and 1) → DCl + D reaction

In this study, we have employed the time-independent close-coupling method for comprehensive calculation of the state-to-state cross sections for the Cl(2P) + D2(v = 0, j = 0 and 1) reaction, including all couplings arising from the nonzero electronic orbital and spin angular momenta of the chlorine atom. The optimization of homonuclear exchange symmetry is incorporated in our calculation. The theoretical results clearly reveal the breakdown of the Born-Oppenheimer (BO) approximation, which is similar to that observed in the Cl + H2 reaction. However, it was found that reducing the coupling terms between electronic states affects the numerical convergence of this reaction. Further calculations for the rotationally excited reagent indicated that rotational excitation enhances the reactivity of Cl(P3/22), whereas it appears to be independent of Cl(P1/22). This behavior suggests reduced non-BO effects in the rotationally excited state reagent for j = 1. Moreover, our predictions align well with recent crossed molecular beam experiments and provide explanations for the experimental observations.