Quasi-classical trajectory study of the reaction N(4S) + H2 and its reverse reaction: Role of initial vibrational and rotational excitations in chemical stereodynamics

Abstract

To investigate the effects of reagent vibrational and rotational states on the stereodynamical properties of the N(4S) + H2(v, j) → NH + H reaction and its reverse reaction of H(2S) + NH(v, j) → N(4S) + H2, we reported a detailed quasiclassical trajectory study using the 4A″ double many-body expansion potential energy surface and at the collision energy of 35 kcal/mol. The density distribution of P(θ r) as a function of the angle between \(\boldsymbol{k}\) and \(\boldsymbol{j^\prime} \), and that of P(ϕ r) as a function of the dihedral angle between the plane containing \(\boldsymbol{k}\)–\({\boldsymbol{k^\prime}} \) and the plane containing \(\boldsymbol{k^\prime}\)–\(\boldsymbol{j^\prime} \), the normal differential cross-sections as well as the averaged product rotational alignment parameter \(\left\langle {P_2 \left({\boldsymbol{j^\prime} \cdot \boldsymbol{k}} \right)} \right\rangle \) are calculated and reported. Comparison between the two reactions has showed that the degrees of alignment and orientation of products related to reagent rovibrational state have marked differences for the two reactive systems. The calculated average rotational alignment parameter \(\left\langle {P_2 \left({\boldsymbol{j^\prime} \cdot \boldsymbol{k}} \right)} \right\rangle \) as a function of the initial vibrational and rotational quantum numbers for the N(4S) + H2 and NH + H(2S) reactions, illustrating the dependence of the product alignment on initial vibrational and rotational excitations.