Near-IR photodissociation of peroxy acetyl nitrate
- 1Department of Chemistry, University of California at Irvine, Irvine, CA 92697, USA
- 2Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA
- 3Division of Geological and Planetary Sciences and Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA, 91125, USA
Abstract. 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 (Jnear-IR≈3x10-8s-1 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 Jnear-IR≈10-5s-1 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 4νCH the lowest overtone excitation with a high photodissociation yield (as opposed to 2νOH in PNA).