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DISSOCIATION DYNAMICS OF VIBRATIONALLY EXCITED TRANS-PERP HOONO

Please use this identifier to cite or link to this item: http://hdl.handle.net/1811/21449

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Title: DISSOCIATION DYNAMICS OF VIBRATIONALLY EXCITED TRANS-PERP HOONO
Creators: Konen, Ian M.; Pollack, Ilana B.; Li, Eunice X. J.; Lester, Marsha I.
Issue Date: 2004
Abstract: Peroxynitrous acid (HOONO) is formed by the reaction of OH and $NO_{2}$ in conjunction with the more stable isomer, nitric acid ($HONO_{2}$). Determination of the HOONO binding energy is essential for atmospheric models to correctly budget these two reactive radical species. We have used an infrared pump-ultraviolet probe technique to obtain an accurate measurement of the binding energy of the trans perp (tp) conformer. The OH ($v = 0$) rotational state distribution resulting from vibrational predissociation of tp-HOONO ($2\nu_{OH}$) was measured by saturated laser induced fluorescence, and found to be consistent with a statistical model. A dissociation energy of 16.2 kcal/mol was obtained from the best fit of the data to a prior distribution, and is complemented by the value inferred from the highest energy channel with observable population. This information, combined with an ab initio calculation of 3.4 kcal/mol for the relative conformational $stability,^{a}$ provides an estimate of 19.6 kcal/mol for the binding energy of the more stable cis-cis (cc) conformer. Additional insight into the decay dynamics is provided by the $0.2 cm^{-1}$ linewidth observed in the IR spectrum. A discussion is presented on the likely origin of this homogeneous broadening (corresponding to a 30 ps lifetime) in terms of intramolecular vibrational redistribution (IVR) and unimolecular dissociation.
URI: http://hdl.handle.net/1811/21449
Other Identifiers: 2004-TI-02
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