Experimental intercomparison of the absorption cross-sections of nitrous acid (HONO) in the ultraviolet and mid-infrared spectral regions

• Published in: Journal of quantitative spectroscopy & radiative transfer 2009-03, Vol.110 (4), p.256-263
• Main Authors: Gratien, A., Lefort, M., Picquet-Varrault, B., Orphal, J., Doussin, J.-F., Flaud, J.-M.
• Format: Article
• Language: English
• Subjects: Absorption cross-sections; HONO; Infrared; Nitrous acid; Ultraviolet
• ISSN: 0022-4073; 1879-1352
• DOI: 10.1016/j.jqsrt.2008.11.003

Nitrous acid, HONO, is an important trace gas in tropospheric photochemistry, because it is a source of OH radicals. In order to obtain HONO concentrations from spectroscopic measurements, the knowledge of accurate absorption cross-sections is essential. Furthermore, the ultraviolet absorption cross-sections of HONO determine its atmospheric photolysis rates, which are still being debated. In particular, in a recent field study focusing on the photolysis frequency of HONO, the absolute values of the ultraviolet absorption cross-sections have been proposed as a potential source for systematic errors. For these reasons, we have compared the absorption cross-sections for HONO in the infrared (IR) and ultraviolet (UV) by performing simultaneous measurements in both spectral regions. Assuming that the IR cross-sections (that show good agreement between different studies) are correct, our study shows a good agreement between the consistent infrared studies and some selected accurate UV spectra published previously (about 6%) while a rather large disagreement (about 22%) is observed when using other UV data sets.