TEMPERATURE-DEPENDENT RATE COEFFICIENT FOR THE CL+CLONO2 REACTION

The rate coefficient for reaction 1, Cl + ClONO2 --> products was meas ured between 195 and 354 K. Cl atoms were generated by pulsed laser ph otolysis of Cl-2 in an excess of ClONO2. The temporal profiles of Cl a tom loss and NO3 product formation were monitored using resonance fluo rescence and tunable diode laser absorption at 662 nm, respectively, T he long path absorption system was used to measure k(1) between 200 an d 298 K while the resonance fluorescence system was employed between 1 95 and 354 K. Thermal decomposition of ClONO2 prevented measurements a t temperatures greater than 354 K. The two techniques yielded rate coe fficients which are in excellent agreement, An Arrhenius rate coeffici ent expression of k(1) = (6.0 +/- 0.4) x 10(-12) exp[(140 +/- 30)/T] c m(3) molecule(-1) s(-1) and room temperature rate constant of k(1)(298 K) (9.6 +/- 1.0) x 10(-12) cm(3) molecule(-1) s(-1) were derived from data at T less than or equal to 298 K. The quoted error limits are 2 sigma and include estimated systematic errors. Our results are compare d with previous measurements, and values of k(1) for atmospheric model ing are recommended.