Laboratory Studies on the Reactions between Chlorine, Sulfur Dioxide, and Oxygen: Implications for the Venus Stratosphere

The title reaction was studied by photolyzing mixtures of Cl_2 and SO_2 with and without O_2 present in an atmosphere of N_2, using Fourier transform infrared spectrophotometry to monitor reactants and products. In the absence of oxygen, sulfur dioxide is quantitatively converted to sulfuryl chloride. With 10 to 150 Torr O_2 present H_2SO_4 is produced as well as SO_2Cl_2. When a number of speculative reactions inferred from these experiments are added to a published model for Venus stratospheric chemistry, it emerges that SO_2Cl_2 is a key reservoir species for chlorine and that the reaction between Cl and So_2 provides an important cycle for destroying O_2 and converting SO_2 to H_2SO_4. The modified model could provide a possible solution to the photochemistry of the Venus stratosphere if the mixing ratio of chlorine on Venus were as high as 8 ppm