The Journal of
Physical Chemistry
0 Copyright, 1983, by the American Chemical Society
VOLUME 87, NUMBER 7
MARCH 31, 1983
LETTERS Low-Temperature Infrared Spectrum of Chlorine Nitrate and Evidence for the Existence of ClOONO S. C. Bhatla,t M. George-Taylor,* C. W. Merldeth,t and J. H. Hall, The School of Geophyslcal Sciences, Atmospheric Sciences Program, Georgia Institute of Technology, Atlanta, Georgia 30332 and, Atlanta University Center Sclence Research Institute, and Department of Chemistry, Atlanta University, Atlanta, Georgia 30314 (Received: October 8, 1982; I n Final Form: February 14, 1983)
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We report the matrix-isolated-infraredspectra of chlorine nitrate. The spectra of both synthetic chlorine nitrate and chlorine nitrate produced in the C10 + NO2+ M products + M reaction show infrared absorptions which may be associated with CIONOz and ClOONO isomers. The infrared absorption frequencies for ClOONO are assigned.
Introduction The possible role of chlorine nitrate in stratospheric ozone chemistry was first pointed out by Rowland and Spencer.' These authors suggested that C10N02 may act to lower the net ozone depletion in the C10, catalytic cycle by providing a sink for the C10 molecule via the reaction C10 + NOz (+M) C10N02 (+M). Consequently, the photolysis products and photochemical lifetime of CIONOz have generated considerable interest since they would play a crucial role in the ultimate impact of CIONOz on the C10, ozone depletion cycle. However, Smith et a1.2 and Chang et al.3 obtained conflicting experimental evidence for the photolysis products. The former measured ClONO + 0 and the latter, using the VLPP technique, measured C1+ NO3 as the products of ClN03decomposition. These results led Molina et al.* to propose four isomers (A-C) for C1ONOZ. Recently, however, Molina et aL4have porposed that a short photochemical lifetime of C10N02decreases its importance as a sink for C10. However, there is no direct evidence for the presence of one or more iso-
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'Atlanta University Center Science Research Institute. *Atlanta University. * Address correspondence to this author at the Georgia Institute of Technology. 0022-365416312087-1091$01.50/0
mers of chlorine nitrate. In this study, we employ the technique of matrix-isolation-infrared spectroscopy to isolate CIONOz in an attempt to isolate and identify isomers. The first set of experiments involved taking the low-temperature infrared spectra of synthetic chlorine nitrate at various dulution ratios while, in a second set of experiments, the chlorine nitrate was produced by the gas-phasereaction of C10 with NOz. The matrix-isolation method is a well-known tech(1) Rowland, F. S.; Spencer, J. E.; Molina, M. J. J . Phys. Chem. 1976, 80,2711. (2)Smith, W.S.; Chou, C. C.; Rowland, F. S.Geophys. Res. Lett. 1977, 4 , 517. (3) Chang, J. S.; Barker, J. R.; Davenport, J. E.; Golden, D. M. Chem. Phys. Lett. 1979, 60, 385. (4) Molina, M. J.; Molina, L. T.; Iahlwata, T. J. J . Phys. Chem. 1980, 84, 3100.
0 1983 American Chemical Society
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The Journal of Physical Chemistry, Vol. 87, No. 7, 1983
Letters
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Figure 1. Gas-phase kinetic cell and cryogenic cell.
nique for the isolation and identification of transient species (e.g., free radicals). However, as discussed in previous publication^,^^^ we have modified this method in order to study gas-phase reaction products. It is important to note that the products from our second set of experiments, referred to above, are from gas-phase reactions in a kinetic cell of design similar to typical kinetic cells used in rate-constant measurements (Figure 1). Furthermore, it is a well-known fact that only reactions involving intracage intramolecular rearrangements or migration of oxygen or hydrogen atoms occur in a 10 K matrix. Hence, our results may be directly applied to stratospheric chemical reactions in the exact same sense as kinetic rate data. The detailed experimental procedure is given in ref 5 and 6.
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