State-to-State Dynamics of H + O₂ Reaction, Evidence for Nonstatistical Behavior

Abstract

Converged differential and integral cross sections are reported for the H + O2 --> OH + O reaction on an improved potential energy surface of HO2(X2A'') using a dynamically exact quantum wave packet method and Gaussian weighted quasi-classical trajectory method. The complex-forming mechanism is confirmed by strong forward and backward scattering peaks and by highly inverted OH rotational state distributions. Both the quantum and classical results provide strong evidence for nonstatistical behavior in this important reaction.

Extraction of state-to-state reactive scattering attributes from wave packet in reactant Jacobi coordinates

“…It is often believed that the product state-resolved information has to be extracted at a projection plane far into the asymptotic region, 26,21 which may lead to huge grid range requirement for a state-to-state calculation. To examine this issue, the total reaction probabilities calculated by both the flux and state-to-state methods are compared in Fig.…”

“…[20][21][22][23] Taking advantage of a L-shaped grid to propagate in reactant coordinates, this collocation method is efficient and accurate and has been successfully applied to calculate state-to-state DCSs for the H+HD, F+H 2 , H + NH, H + ND, 24 H+O 2 , 20,21 and O + O 2 reactions. 25 The L-shaped grid method saves a large number of grid points, as compared with a conventional rectangular grid, which makes this RCB wave packet method particularly attractive and presents an efficient alternative to the PCB approaches.…”

A Quasiclassical Trajectory Study of the Reaction of H Atoms with O2(1Δg)

“…Due to its importance, the reaction has been the subject of a large number of studies, both experimental and theoretical. 2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27 A large body of information is available on the reaction of H atoms with oxygen molecules in the electronic ground state,…”

Classical versus quantum vibrational state distributions for the benchmark polyatomic reaction OH+D2: Checking the validity of the QCT method

“…To deal with vibrational quantization in the products within the QCT method, we used the GB procedure [17][18][19][20][21][22][23][24][25][26][27][28] which can be summarized as follows: Bohr's basic idea is that only the classical paths corresponding to integer actions of the final products should be permitted. This is also an idea to which the classical S matrix theory (CSMT) of Miller and Marcus leads [32][33][34][35][36][37][38].…”

“…When in the QCT calculations the standard binning (SB) procedure (which amounts to attribute the same statistical weight to each trajectory) was used, the experimental product vibrational state populations were not reproduced [6][7][8][9]. However, using the Gaussian binning (GB) procedure, which takes into account Bohr quantization principle for vibrational energies [17][18][19][20][21][22][23][24][25][26][27][28], made the expected product state spectrum appear, for the first time as far as polyatomic processes are concerned [10]. However, this method (QCT-GB) gives a population of the (1, 1) state of 3%, much lower than the experimental value, 11% [10].…”