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The kinetics of the reaction of NO 2 with 03 have been investigated at 296 K, using UV absorption spectroscopy to monitor decay of NO 2 or O 3 and infrared laser absorption spectroscopy to monitor formation of the reaction product N 20 s . The results both for the rate eoeffig/iont at 296 K (k I = 3.5 x 10 -t7 ems molecule -t s -t ) and the reaction stoiehiomel~y (ANO2/AO3 = 1.85 -+ 0.09) are in good agreement with previous studies, confirming that the two step mechanism involving formation of symmetrical NO 3 as an intermediate is predominant.A possible minor role for the unsymmetrical ONOO species is suggested to account for the lowerthan-expected stoichiometry factor. The importance of this reaction in the oxidation of atmospheric NO2 is discussed.

Diode laser spectroscopy has been employed to monitor the formation of chlorine nitrate (CIONO,) in the association reaction of C10 with NOz. Chlorine nitrate is the only stable end-product of this reaction at room temperature. Time-resolved measurements of CIONO, formation using molecular modulation showed no evidence for any involvement of unstable isomers of C1NO3 in the reaction. These measurements gave a value of k, = (1.8 ? 0.4) x cm6/molecule2 . s for the reactionat 295 K and an upper limit of 5 ms for the lifetime of any isomeric products at this temperature.

Chlornitrat erweist sich als einziges stabiles Endprodukt der Reaktion Abei 20°C. Zeitaufgelöste Messungen der Chlornitratbildung mit Hilfe von Molekularmodulation ergeben keinen Hinweis auf die Beteiligung instabiler Isomerer des ClNO3 an der Reaktion.

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