Static SIMS studies of reactions on mimics of polar stratospheric clouds II:: Low-temperature, low-pressure interactions of Cl2 and Cl2O with solid ice films

The interactions of molecular chlorine, dichlorine monoxide, and hypochlorous acid with solid ice films have been examined. At 90-100 K, chlorine can be made to condense as a molecular solid, forming a discrete layer on top of an existing film of solid H2O. interaction between the Cl-2 and the water molecules is minimal. At temperatures above approximately 130 K, the Cl-2 and water react to produce a mixed film of water, hypochlorous acid, and solvated HCl. As with chlorine, the dichlorine monoxide did not react with water at 90 K. However, there was evidence of a hydrogen-bond-like interaction between the Cl2O and H2O molecules. Upon warming to 120 K or higher, the two reacted to produce a mixed film of hypochlorous acid and water. The reactions that occurred at the higher temperatures are of interest because of the well-documented influence of polar stratospheric clouds, which consist of solid water or water/nitric acid particles, on the release of active chlorine species into the stratosphere.