State-to-state dynamics of H+HX collisions. I. The H+HXH2+X (X = Cl,Br,I) abstraction reactions at 1.6 eV collision energy

Article abstract of DOI:10.1063/1.456574

The rotational and vibrational state distributions of the H2 product from the reactions of translationally excited H atoms with HCl, HBr, and HI at 1.6 eV are probed by coherent anti-Stokes Raman scattering spectroscopy after only one collision of the fast H atom.Despite the high collision energy, only the very exoergic (ΔH = -1.4 eV) hydrogen atom abstraction involving HI leads to appreciable H2 product vibrational excitation.For this reaction the H2 vibrational distribution is strongly inverted and peaks in v' = 1, with 25percent of the total available energy partitioned to vibration.For the mildy exoergic (ΔH = -0.72 eV) reaction with HBr and the nearly thermoneutral (ΔH = -0.05 eV) reaction with HCl, very little energy appears in H2 vibration, 9percent and 2percent, respectively, and the vibrational state distributions peak at v' = 0.However, in all three reactions a significant fraction, 18percent to 21percent, of the total energy available appears as H2 rotation.All three reactions show a strong propensity to conserve the translational energy, that is the translational energy of the H2+X products is very nearly the same as that of the H+HX reactants.For the reactions with HCl, HBr, and HI the average translational energy of the products is 1.3, 1.7, and 1.7 eV. respectively, and the width of the translational energy distribution is only about 0.5 eV full width at half maximum.The energy disposal in all three reactions is quite specific, despite the fact that this high collision energy is well above the barrier to reaction in all three systems and a large number of product quantum states are energetically accessible.Only a few of these energetically allowed final states are appreciably populated.Although detailed theoretical calculations will be required to account completely for the state specifity, quite simple models of the reaction dynamics can explain much of the dynamical bias that we observe.

Full text of DOI:10.1063/1.456574

Statetostate dynamics of H+HX collisions. I. The H+HXH2+X (X=Cl,Br,I) abstraction
reactions at 1.6 eV collision energy
Pamela M. Aker, Geoffrey J. Germann, and James J. Valentini
Citation: The Journal of Chemical Physics 90, 4795 (1989); doi: 10.1063/1.456574
View online: http://dx.doi.org/10.1063/1.456574
View Table of Contents: http://scitation.aip.org/content/aip/journal/jcp/90/9?ver=pdfcov
Published by the AIP Publishing
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