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Title: Mode specificity in the HF + OH → F + H{sub 2}O reaction

Abstract

Full-dimensional quantum dynamics and quasi-classical trajectory calculations are reported for the title reaction on a recently constructed ab initio based global potential energy surface. Strong mode specificity was found, consistent with the prediction of the sudden vector projection model. Specifically, the HF vibration strongly promotes the reaction while the OH vibration has little effect. Rotational excitations of both reactants slightly enhance the reaction.

Authors:
; ;  [1]
  1. Department of Chemistry and Chemical Biology, University of New Mexico, Albuquerque, New Mexico 87131 (United States)
Publication Date:
OSTI Identifier:
22310757
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 141; Journal Issue: 16; Other Information: (c) 2014 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; EXCITATION; FORECASTING; HYDROFLUORIC ACID; HYDROXYL RADICALS; POTENTIAL ENERGY; SPECIFICITY; WATER

Citation Formats

Song, Hongwei, Li, Jun, and Guo, Hua, E-mail: hguo@unm.edu. Mode specificity in the HF + OH → F + H{sub 2}O reaction. United States: N. p., 2014. Web. doi:10.1063/1.4900445.
Song, Hongwei, Li, Jun, & Guo, Hua, E-mail: hguo@unm.edu. Mode specificity in the HF + OH → F + H{sub 2}O reaction. United States. doi:10.1063/1.4900445.
Song, Hongwei, Li, Jun, and Guo, Hua, E-mail: hguo@unm.edu. 2014. "Mode specificity in the HF + OH → F + H{sub 2}O reaction". United States. doi:10.1063/1.4900445.
@article{osti_22310757,
title = {Mode specificity in the HF + OH → F + H{sub 2}O reaction},
author = {Song, Hongwei and Li, Jun and Guo, Hua, E-mail: hguo@unm.edu},
abstractNote = {Full-dimensional quantum dynamics and quasi-classical trajectory calculations are reported for the title reaction on a recently constructed ab initio based global potential energy surface. Strong mode specificity was found, consistent with the prediction of the sudden vector projection model. Specifically, the HF vibration strongly promotes the reaction while the OH vibration has little effect. Rotational excitations of both reactants slightly enhance the reaction.},
doi = {10.1063/1.4900445},
journal = {Journal of Chemical Physics},
number = 16,
volume = 141,
place = {United States},
year = 2014,
month =
}
  • Essentially exact quantum mechanical calculations are carried out to determine the energies and lifetimes of the quasi-bound states for a system of two (non~linearly) coupled oscillators (one of which is harmonic, the other being able to dissociate). For weak coupling the system displays mode-specificity, i.e., the unimolecular rate constants are not a monotonic function of the total energy, but increased coupling and frequency degeneracy tends to destroy mode-specificity. A somewhat surprising result is that for a given coupling the degree of modespecificity is roughly independent of the energy, in marked contrast to the fact that there is an energetic thresholdmore » for the onset of "stochastic trajectories" of the corresponding classical system; i.e., there seems to be no relation between statistical/mode-specific behavior of the unimolecular rate constants and stochastic/regular classical trajectories. In order to be able to treat more physically relevant models--i.e., those with more than two degrees of freedom--a semiclassical model is constructed and seen to be able to reproduce the accurate quantum mechanical rates reasonably well.« less
  • Energies and lifetimes (with respect to tunneling) for metastable states of the Henon-Heiles potential energy surface [V(x,y) = 1/2 x{sup 2} - 1/3 x{sup 3} + 1/2 y{sup 2} + xy{sup 2}] have been computed quantum mechanically (via the method of complex scaling). This is a potential surface for which the classical dynamics is known to change from quasiperiodic at low energies to ergodic-like at higher energies. The rate constants (i.e. inverse lifetimes) for unimolecular decay as a function of energy, however, are seen to be well described by standard statistical theory (microcanomical transition state theory, RRKM plus tunneling) overmore » the entire energy region, This is thus another example indicating that mode-specificity in unimolecular reaction dynamics is not determined solely by the quasiperiodic/ergodic character of the intramolecular mechanics.« less
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  • Essentially exact quantum mechanical calculations are carried out to determine the energies and lifetimes of the quasibound states for a system of two (nonlinearly) coupled oscillators (one of which is harmonic, the other being able to dissociate). For weak coupling the system displays mode specificity, i.e., the unimolecular rate constants are not a monotonic function of the total energy, but increased coupling and frequency degeneracy tends to destroy mode specificity. A somewhat surprising result is that for a given coupling the degree of mode specificity is roughly independent of the energy, in marked contrast to the fact that there ismore » an energetic threshold for the onset of ''stochastic trajectories'' of the corresponding classical system: i.e., there seems to be no relation between statistical/mode-specific behavior of the unimolecular rate constants and stochastic/regular classical trajectories. In order to be able to treat more physically relevant models; i.e., those with more than two degrees of freedom, a semiclassical model is constructed and seen to be able to reproduce the accurate quantum mechanical rates reasonably well.« less