Temperature dependent rate coefficient for the Cl + ClONO₂ reaction

The rate coefficient for reaction 1, Cl + ClONO₂ → products was measured between 195 and 354 K. Cl atoms were generated by pulsed laser photolysis of Cl₂ in an excess of ClONO₂. The temporal profiles of Cl atom loss and NO₃ product formation were monitored using resonance fluorescence and tunable diode laser absorption at 662 nm, respectively. The long path absorption system was used to measure k₁ between 200 and 298 K while the resonance fluorescence system was employed between 195 and 354 K. Thermal decomposition of ClONO₂ prevented measurements at temperatures greater than 354 K. The two techniques yielded rate coefficients which are in excellent agreement. An Arrhenius rate coefficient expression of k₁ = (6.0 ± 0.4) × 10^-12 exp[(140 ± 30)/T] cm³ molecule^-1 s^-1 and room temperature rate constant of k₁(298 K) = (9.6 ± 1.0) × 10^-12 cm³ molecule^-1 s^-1 were derived from data at T ≤ 298 K. The quoted error limits are 2σ and include estimated systematic errors. Our results are compared with previous measurements, and values of k₁ for atmospheric modeling are recommended.