Effect of HCl addition and temperature on the heterogeneous chemistry and photochemistry of ClONO2 adsorbed on ice crystals

The heterogeneous chemistry and photochemistry of chlorine nitrate adsorbed on HCl-doped crystals was studied mainly at 181 K and at 190 K. Under our experimental conditions the main gaseous products found at 181 K were Cl2O and Cl-2, while at 190 K, Cl2O was mainly observed. At both temperatures a net enhancement in the rate of gaseous product formation was observed when light of wavelength longer than 350 mn entered the reactor. The obtained re sults in conditions where the ClONO2 concentration is higher than HCl conce ntration, and both are high enough to maintain saturation of the surface, s howed that the rate of gaseous products formation at 181 K depends on the r eactive species adsorbed while at 190 K, it is independence of them. The im plications of these findings to the polar stratospheric chemistry are brief ly discussed.