Time-dependent wave packet study of the $N++H2$ reaction

The time-dependent wave packet method has been used to calculate initial state selected reaction probabilities, reaction cross sections, and rate constants for the $N++H2$ reaction on the potential energy surface of Wilhelmsson, Siegbahn, and Schinke [J. Chem. Phys. 96, 8202 (1992)]. In addition to providing results that can be used to test more approximate theories, these calculations are used to shed light on a number of key issues concerning the reaction, including the correct value of the reaction endothermicity, the reactivity of excited $H2$ rotational states, and the lifetimes of the intermediate $NH2+$ complexes that are formed in collisions of $N+$ with $H2(v=0)$ and $H2(v=1).$ We also show that an earlier quasiclassical trajectory study of the reaction on the same potential energy surface predicted the wrong cross-section behavior in the threshold region as a result of an incorrect treatment of product zero-point energy.