Chlorine nitrate: Kinetics of formation by ClO+NO2+M and of reaction with OH

Kinetic studies by the discharge–flow technique are reported. For ClONO2 formation from T=250–365 K, ClO decays in excess NO2 are monitored by conversion of ClO to Cl followed by resonance fluorescence detection at 134.7 nm. For OH reaction over T=246–387 K, pseudo-first-order OH decays are observed directly by OH-resonance fluorescence. The recombination reaction (1) is near its low pressure, third-order limit with k1= (0.83±0.12) ×10−31 cm6 s−1 at 300 K for M=He and (1.52±0.23) ×10−31 cm6 s−1 at 297 K for M=N2. The k1,He temperature dependence corresponds to T−3.15. These results are in good agreement with those of other studies. A temperature- and pressure-dependent, empirical rate constant expression for stratospheric modeling calculations is proposed. The rate constant k2 for the OH reaction is found to be (1.19±0.10) ×10−12 exp[(−333 ±22)/T] cm3 s−1, i.e., (3.93±0.11) ×10−13 at 295 K. The results are compared with other measurements and their significance for stratospheric processes is discussed.