ACP Atmospheric Chemistry and Physics ACP 1680-7324 Copernicus GmbH Göttingen, Germany 10.5194/acp-10-6137-2010 UV absorption cross sections of nitrous oxide (N<sub>2</sub>O) and carbon tetrachloride (CCl<sub>4</sub>) between 210 and 350 K and the atmospheric implications Rontu Carlon N. 1 2 Papanastasiou D. K. 1 2 Fleming E. L. 3 4 Jackman C. H. 3 Newman P. A. 3 Burkholder J. B. 1 Earth System Research Laboratory, Chemical Sciences Division, National Oceanic and Atmospheric Administration, 325 Broadway, Boulder Colorado, 80305-3328, USA Cooperative Institute for Research in Environmental Sciences, University of Colorado, Boulder Colorado, 80309, USA NASA Goddard Space Flight Center, Greenbelt, MD, 20771, USA Science Systems and Applications, Inc., Lanham, MD, 20706, USA 07 07 2010 10 13 6137 6149 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/10/6137/2010/acp-10-6137-2010.html The full text article is available as a PDF file from http://www.atmos-chem-phys.net/10/6137/2010/acp-10-6137-2010.pdf

Absorption cross sections of nitrous oxide (N<sub>2</sub>O) and carbon tetrachloride (CCl<sub>4</sub>) are reported at five atomic UV lines (184.95, 202.548, 206.200, 213.857, and 228.8 nm) at temperatures in the range 210–350 K. In addition, UV absorption spectra of CCl<sub>4</sub> are reported between 200–235 nm as a function of temperature (225–350 K). The results from this work are critically compared with results from earlier studies. For N<sub>2</sub>O, the present results are in good agreement with the current JPL recommendation enabling a reduction in the estimated uncertainty in the N<sub>2</sub>O atmospheric photolysis rate. For CCl<sub>4</sub>, the present cross section results are systematically greater than the current recommendation at the reduced temperatures most relevant to stratospheric photolysis. The new cross sections result in a 5–7% increase in the modeled CCl<sub>4</sub> photolysis loss, and a slight decrease in the stratospheric lifetime, from 51 to 50 years, for present day conditions. The corresponding changes in modeled inorganic chlorine and ozone in the stratosphere are quite small. A CCl<sub>4</sub> cross section parameterization for use in atmospheric model calculations is presented.

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