Kinetics of the reactions of ClO with O and with NO

The ClO+O(k2) and ClO+NO(k3) reaction rate constants were obtained by measurements of steady-state Cl-atom concentrations using resonance fluorescence at 134.7 nm in a discharge-flow system. ClO is made by the Cl+O3(k1) reaction and removed by either added O or NO whose concentrations are measured independently. Over the temperature range of 220 or 230–298 K, k2/k1= (1.55±0.17) exp[(246±30)/T] and k3/k1= (0.52±0.05) exp[(373±23/T]. Combined with k1= (2.17±0.18) ×10−11 exp[−(171±20)/T] cm3 sec−1 reported earlier, this yields k2= (3.38±0.50) ×10−11 exp[(75±40)/T] and k3= (1.13±0.14) ×10−11 exp[(200±30)/T] cm3 sec−1. The Cl+O3 reaction was reinvestigated and k1 found to be (2.12±0.11) ×10−11 exp[−(157±12)/T] cm3 s−1, in excellent agreement with the earlier value. The kinetic and stratospheric significance of these findings is discussed.