ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-5-385-2005 Near-IR photodissociation of peroxy acetyl nitrate Nizkorodov S. A. 1 Crounse J. D. 2 Fry J. L. 2 Roehl C. M. 3 Wennberg P. O. 3 Department of Chemistry, University of California at Irvine, Irvine, CA 92697, USA Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA Division of Geological and Planetary Sciences and Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA 10 02 2005 5 2 385 392 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys.net/5/385/2005/acp-5-385-2005.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/5/385/2005/acp-5-385-2005.pdf

Measurements of the C-H overtone transition strengths combined with estimates of the photodissociation cross sections for these transitions suggest that near-IR photodissociation of peroxy acetyl nitrate (PAN) is less significant (<i>J</i><sub>near-IR</sub>&asymp;3x10<sup>-8</sup>s<sup>-1</sup> at noon) in the lower atmosphere than competing sinks resulting from unimolecular decomposition and ultraviolet photolysis. This is in contrast to the photochemical behavior of a related peroxy nitrate, pernitric acid (PNA), that undergoes rapid near-IR photolysis in the atmosphere with <i>J</i><sub>near-IR</sub>&asymp;10<sup>-5</sup>s<sup>-1</sup> at noon (Roehl et al., 2002). This difference is attributed to the larger binding energy and larger number of vibrational degrees of freedom in PAN, which make 4&nu;<sub>CH</sub> the lowest overtone excitation with a high photodissociation yield (as opposed to 2&nu;<sub>OH</sub> in PNA).