Second OH overtone excitation and statistical dissociation dynamics of peroxynitrous acid

Abstract

The second OH overtone transition of the trans-perp conformer of peroxynitrous acid (tp-HOONO) is identified using infrared action spectroscopy. HOONO is produced by the recombination of photolytically generated OH and NO(2) radicals, and then cooled in a pulsed supersonic expansion. The second overtone transition is assigned to tp-HOONO based on its vibrational frequency (10 195.3 cm(-1)) and rotational band contour, which are in accord with theoretical predictions and previous observations of the first overtone transition. The transition dipole moment associated with the overtone transition is rotated considerably from the OH bond axis, as evident from its hybrid band composition, indicating substantial charge redistribution upon OH stretch excitation. The overtone band exhibits homogeneous line broadening that is attributed to intramolecular vibrational redistribution, arising from the coupling of the initially excited OH stretch to other modes that ultimately lead to dissociation. The quantum state distributions of the OH X (2)Pi (nu=0) products following first and second OH overtone excitation of tp-HOONO are found to be statistical by comparison with three commonly used statistical models. The product state distributions are principally determined by the tp-HOONO binding energy of 16.2(1) kcal mol(-1). Only a small fraction of the OH products are produced in nu=1 following the second overtone excitation, consistent with statistical predictions.

Spectroscopic identification and stability of the intermediate in the OH + HONO 2 reaction

“…The prior distribution assumes that the product states associated with the translational, rotational, and vibrational motions of the OH and HONO 2 fragments are populated with equal probability subject only to a constraint on the energy available to products, E avail ϭ h IR Ϫ D 0 (23). In this experiment, 3.…”

HONO and NO<sub>2</sub> evolution from irradiated nitrate-doped ice and frozen nitrate solutions

“…HOONO 2 may decompose to yield NO 2 or HONO (Zhu et al, 1993;Dentener et al, 2002). The thermal and photolytic decay of HOONO yields NO 2 (Konen et al, 2005). This would imply that the photolysis of either peroxide either in the UV region or at higher wavelengths might contribute to NO 2 fluxes.…”

Dynamics and spectroscopy of vibrational overtone excited glyoxylic acid and 2,2-dihydroxyacetic acid in the gas-phase

“…20,40,41 In spite of the much lower photoabsorption cross sections for vibrational overtone transitions when compared with electronic transitions, [42][43][44] this chemistry initiated by vibrational overtone pumping in ground electronic states is important in the atmosphere. [6][7][8]20,40,41, Fast reactions, where energy dissipation is comparatively slow, are of considerable interest in environmental applications. 1,20,73 In this spirit, we present results of a study on the early time dynamics of the concerted reactions initiated by excitation of the OH vibrational overtone transition of GA and its monohydrate, 2,2-dihydroxyacetic acid ͑GAM͒.…”

“…Light initiated processes provide attractive systems for studying state specific unimolecular reactions since photon absorption generates activated complexes with a narrow distribution of internal energy. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20] Unimolecular reactions are traditionally treated with statistical approaches such as Rice-Ramsperger-Kassel-Marcus Theory ͑RRKM͒, which assumes that coupling within the activated complex is sufficiently strong to distribute excitation energy between all vibrational modes on a fast time scale compared with reaction. 19,[21][22][23][24][25] Several classic studies using reactions initiated by excitation of vibrational overtone transitions near a chemical threshold were performed in a search for control over these reactions.…”