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

• Published in: Proceedings of the National Academy of Sciences - PNAS 2008-09, Vol.105 (35), p.12678
• Main Authors: O'Donnell, Bridget A, Li, Eunice X J, Lester, Marsha I, Francisco, Joseph S
• Format: Article
• Language: English
• Subjects: Acids; Chemical reactions; Chemistry; Nitrogen; Spectrum analysis
• ISSN: 0027-8424; 1091-6490

The reaction of nitric acid with the hydroxyl radical influences the residence time of ... in the lower atmosphere. Prior studies [Brown SS, Burkholder JB, Talukdar RK, Ravishankara AR (2001) J Phys Chem A 105:1605-1614] have revealed unusual kinetic behavior for this reaction, including a negative temperature dependence, a complex pressure dependence, and an overall reaction rate strongly affected by isotopic substitution. This behavior suggested that the reaction occurs through an intermediate, theoretically predicted to be a hydrogen-bonded OH-... complex in a six-membered ring-like configuration. In this study, the intermediate is generated directly by the association of photolytically generated OH radicals with ... and stabilized in a pulsed supersonic expansion. Infrared action spectroscopy is used to identify the intermediate by the OH radical stretch (...) and OH stretch of nitric acid (...) in the OH-... complex. Two vibrational features are attributed to OH- ...: a rotationally structured ... band at 3516.8 cm... and an extensively broadened ... feature at 3260 cm..., both shifted from their respective monomers. These same transitions are identified for OD-... Assignments of the features are based on their vibrational frequencies, analysis of rotational band structure, and comparison with complementary high level ab initio calculations. In addition, the OH (v = 0) product state distributions resulting from ... and ... excitation are used to determine the binding energy of OH-..., D... ≤ 5.3 kcal*mol..., which is in good accord with ab initio predictions. (ProQuest: ... denotes formulae/symbols omitted.)