Control of Mode/Bond Selectivity and Product Energy Disposal by the Transition State: X + H₂O (X = H, F, O(³P), and Cl) Reactions

Abstract

The ability to predict mode/bond selectivity and energy disposal is of central importance for controlling chemical reactions. We argue that the transition state plays a critical role in state-to-state reactivity and propose a simple sudden model based on coupling with the reaction coordinate at the transition state. The applicability of this so-called sudden vector projection (SVP) model is examined for several prototypical atom-triatom, namely, X + H2O (X = H, F, O((3)P), and Cl) reactions. It is shown that the SVP model is capable of qualitatively predicting experimental and full-dimensional quantum dynamical results, including those reported in this work, for these polyatomic reactions. These results, and those for other reactions, suggest that the SVP model offers a general paradigm for understanding quantum state resolved reactivity in bimolecular reactions.

Communication: Equivalence between symmetric and antisymmetric stretching modes of NH3 in promoting H + NH3 → H2 + NH2 reaction

“…On the other hand, fulldimensional quantum models have currently been amenable to the four-atom reactions and such studies have shown that the symmetric and antisymmetric stretching modes of H 2 O have large and nearly equal efficacies in promoting its reactions with H and Cl. [22][23][24][25][26][27] Contrast to CH 4 , however, the stretching modes of H 2 O are singly degenerate. As a result, the observation in the H/Cl + H 2 O reactions does not necessarily help to shed light on the relative efficacies of the two stretching modes in the H/Cl + CH 4 reactions.…”

Vibrationally Promoted Dissociation of Water on Ni(111)

“…The quantum dynamics were represented in Jacobi coordinates (shown in Fig. 1) by a 6D Chebyshev real wave-packet method (20,35). Specifically, an initial wave packet was launched for a rovibrational state of reactant (D 2 O) above the surface and propagated on the PES using the Chebyshev three-term recursion formula.…”

“…The vibrational enhancement of the reactivity can be understood by the recently proposed sudden vector projection (SVP) model, which assumes that the reaction occurs in the sudden limit, and the enhancement of reactivity by a reactant mode reflects its coupling with the reaction coordinate at the transition state (35,44). Such coupling can be estimated by the projection of the reactant mode vector onto the reaction coordinate vector at the transition state.…”

Communication: Imaging the effects of the antisymmetric-stretching excitation in the O(3P) + CH4(v3 = 1) reaction

“…In this regard, the propensity toward translational energy at low collision energies can also be found in many other activated reactions. [29][30][31][35][36][37][38][39][40][41][42][43][44] On intuitive grounds, a finite momentum of the two reactants seems necessary in order to drive reactions over barriers. If correct, a translational propensity in the post-threshold region of activated reactions may well be a general trait; regardless it is an early-, central-, or late-barrier reaction.…”