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Issue 6, 1999
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An abinitio quasi-classical direct dynamics investigation of the F+C2H4→C2H3F+H product energy distributions


A direct dynamics technique, using energies, forces and second derivatives calculated at the UHF/6–31G* level of theory, was used to investigate product energy distributions of the F+C2H4→C2H3F+H collision reaction. The shifting and broadening of the product translational energy distribution as the system moves from the exit-channel barrier to the products was studied. Since properties associated with the rupturing C···H bond are similar for the C2H5 and C2H4F exit-channel barriers, and integration of the C2H5→C2H4+H reaction is approximately 2.5 times faster than the C2H4F→C2H3F+H reaction, trajectories of the former reaction were propagated to gain insight into the exit-channel dynamics. Ensemble averaged results for C2H5 dissociation are well described by a model based on isotropic exit-channel dynamics which assumes that the product relative translational distribution arises from the centrifugal potential and relative translational energy distributions at the exit-channel barrier plus the exit-channel potential release. The width of the product translational energy distribution is sensitive to overall rotational angular momentum and its partitioning between C2H4···H orbital angular momentum and C2H4 rotational angular momentum. The simulated product translational energy distribution for the C2H4F→C2H3F+H reaction is broadened by relative translation–vibrational couplings in the exit-channel and is similar to the distribution used to fit crossed molecular beam data. Approximately 50% of the available energy is in product relative translation, which also agrees with experiment. RRKM calculations indicate that a second reaction mechanism, involving 1–2 hydrogen migration prior to C···H bond fission, does not significantly contribute to C2H3F+H product formation.

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Article type: Paper
DOI: 10.1039/A808650H
Citation: Phys. Chem. Chem. Phys., 1999,1, 999-1011
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    An abinitio quasi-classical direct dynamics investigation of the F+C2H4→C2H3F+H product energy distributions

    K. Bolton, H. Bernhard Schlegel, W. L. Hase and K. Song, Phys. Chem. Chem. Phys., 1999, 1, 999
    DOI: 10.1039/A808650H

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