Quantum Mechanical Calculation of Energy Dependence of OCl/OH Product Branching Ratio and Product Quantum State Distributions for the O(¹D) + HCl Reaction on All Three Contributing Electronic State Potential Energy Surfaces

Abstract

OCl/OH product branching ratios are calculated as a function of total energy for the O( (1) D) + HCl reaction using quantum wavepacket methods. The calculations take account of reaction on all the three electronic state potential energy surfaces which correlate with both reactants and products. Our results show that reaction on the excited electronic state surfaces has a large effect on the branching ratio at higher energies and that these surfaces must therefore be fully taken into account. The calculations use the potential energy surfaces of Nanbu and co-workers. Product vibrational and rotational quantum state distributions are also calculated as a function of energy for both product channels. Inclusion of the excited electronic state potential energy surfaces improves the agreement of the predicted product vibrational quantum state distributions with experiment for the OH product channel. For OCl agreement between theory and experiment is retained for the vibrational quantum state distributions when the excited electronic state potential energy surfaces are included in the analysis. For the rotational state distributions good agreement between theory and experiment is maintained for energies at which experimental results are available. At higher energies, above 0.7 eV of total energy, the OCl rotational state distributions predicted using all three electronic state potential energy surfaces shift to markedly smaller rotational quantum numbers.

ClO Radical Yields in the Reaction of O(1D) with Cl2, HCl, Chloromethanes, and Chlorofluoromethanes

“…O( 1 D) chemistry is particularly interesting from a kinetic and dynamics standpoint due to the potential reaction pathways available. The dynamics of the O( 1 D) reaction with HCl, in particular, has been studied in detail both experimentally , and theoretically − (additional references cited within). The dynamics of O( 1 D) reactions with polyatomic molecules has received less attention .…”

The Dynamics of the O(1D) + HCl → OH + Cl Reaction at a 0.26 eV Collision Energy: A Comparison between Theory and Experiment

“…The excited 1 1 A′′ and 2 1 A′ PESs seem to play a significant role according to the analysis performed at J = 0 of the product branching ratio and vibrational distributions for OH . The study of reaction probabilities, , vibrational distributions, and product internal energy distributions reveals different dynamics in the excited electronic states in comparison with the ground PES. Recent experimental and theoretical investigations of the DCSs concluded, however, that reaction proceeds predominantly via the ground electronic state at collision energies of less than 0.2819 eV (6.5 kcal mol −1 ) …”

“…This circumstance together with the high exoergicity (1.92 eV for reaction ) and the heavy−light−heavy kinematics of the system makes exact quantum methods (EQMs) extremely demanding in terms of computational time, requiring partial waves up to J = 120 and a large basis of rovibrational channels. These numerical difficulties explain why most of the existing theoretical work consists on QCT calculations. − ,,− Quantum mechanical (QM) calculations have been restricted to a zero total angular momentum, J = 0, with different helicity decoupling approximations invoked when the J > 0 case was considered. ,,− …”

The stereodynamics of the O (D-1) plus HCl reaction and its isotopic variants (DCl)

“…The reason is due to their important role in atmospheric chemistry. Among these reactions of halogen-containing molecules, interest in the O ( 1 D) + HCl has grown rapidly both from the experimental [3][4][5][6][7][8][9][10][11] and theoretical [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] viewpoint. From the experimental viewpoint, the branching ratio of the two different product channels (O ( 1 D) + HCl ?…”

“…Theoretically, a number of potential energy surfaces (PESs) [12][13][14][15][16][17][18] were constructed for O ( 1 D) + HCl reaction. Based on these PESs, many of the QCT [12,13,[17][18][19][20][21] and quantum [16,[22][23][24][25][26] calculations were performed on the O ( 1 D)+ HCl reaction system in order to reproduce the experimental results, such as reaction rates, branch ratio of ClO/OH, reaction cross-section, differential cross-section and reaction probabilities. A good agreement was found between the theoretical and experimental results.…”