Near ultraviolet photolysis of HFCO: The H+FCO channel

The technique of H (Rydberg) atom photofragment translational spectroscopy has been used to study the process HFCO(S1)→H+FCO(X̃), near its appearance threshold, at excitation wavelengths ca. 247 nm. Analyses of the resulting total kinetic energy release spectra lead to an accurate determination of t...

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Veröffentlicht in:The Journal of chemical physics 1997-04, Vol.106 (14), p.6198-6201
Hauptverfasser: Reed, Claire L., Kono, Mitsuhiko, Langford, Stephen R., Hancock, Thomas W. R., Dixon, Richard N., Ashfold, Michael N. R.
Format: Artikel
Sprache:eng
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Zusammenfassung:The technique of H (Rydberg) atom photofragment translational spectroscopy has been used to study the process HFCO(S1)→H+FCO(X̃), near its appearance threshold, at excitation wavelengths ca. 247 nm. Analyses of the resulting total kinetic energy release spectra lead to an accurate determination of the C–H bond strength: D0(H–FCO)=34950±20 cm−1. The resulting FCO fragments are observed to be formed with little internal energy, distributed mainly in the form of a-axis rotation. Fragmentation is shown to involve S1–T1 intersystem crossing, followed by rapid passage along the minimum energy path to the eventual H+FCO products. This minimum energy path involves passage over (or H atom tunnelling through) a saddle point, the height of which is ⩾4740 cm−1 above the dissociation asymptote. The observed propensity for a-axis rotation in the FCO product reflects changes in the parent geometry as it evolves along the C–H dissociation coordinate on the T1 surface; past the saddle point, the barrier energy is released largely in the form of product recoil.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.473243