Stratospheric photodissociation of several saturated perhalo chlorofluorocarbon compounds in current technological use (fluorocarbons-13, -113, 114, and -115)

C. C. Chou, R. J. Milstein, W. S. Smith, H. Vera Ruiz, Mario J. Molina, F. S. Rowland
1978 The Journal of Physical Chemistry  
Photon absorption cross sections have been measured in the stratospherically important 1849-2273-A range for CClF3 (fluorocarbon-13), CC12FCClFz (FC-113), CClFzCClF2 (FC-1141, and CClFzCF3 (FC-115). Atmospheric residence times have been calculated for these four compounds, and for CC13F (FC-11) and CC12Fz (FC-121, with the assumption that the molecules are removed only by direct solar photolysis or by reaction with O('D) atoms. Four different eddy diffusion models were used for stratospheric
more » ... ing. Direct photolysis accounts for >90% of the removal of FC-11, >8O% for FC-12 and FC-113, and <20% for FC-13 and FC-115. Direct photolysis and reaction with O(lD) atoms are roughly comparable in importance for the removal of FC-114. The calculated atmospheric residence times range from 40 to 550 years, with especially long calculated residence times for FC-13 and FC-115 which have very low photon absorption cross sections and which are therefore primarily removed from the stratosphere by reaction with O(lD) atoms. Publication costs assisted by the U.S. Department of Energy Bromine nitrate, BrON02, has been synthesized and purified, and its ultraviolet and infrared spectra have been measured. The stratospheric photolysis of BrONOz is about twenty times more rapid than that of the analogous ClONO2. However, since HBr is not as important a sink in the Br0,-catalytic chain for removal of stratospheric ozone as HC1 is for the C10, chain, as much an 10-20% of the Br may be present as BrON02. Measurements of the rate of its formation from BrO + NOz + M are necessary for accurate estimate of the stratospheric importance of BrON02.
doi:10.1021/j100490a001 fatcat:hf3dzjg36jaqhgo2qh3nhtn5gi