PHOTOCHEMISTRY OF CHLORINE DIOXIDE IN POLYCRYSTALLINE ICE (T=140-185 K) - PRODUCTION OF CHLORYL CHLORIDE, CL-(OCLO)

The photochemistry of chlorine dioxide, OClO, in polycrystalline ice h as been investigated at T=140-185 K using FTIR and UV-vis spectroscopy . Photolysis with ultraviolet light at 360 nm produced chloryl chlorid e, Cl-(OClO). The unique vibrational bands at 1210, 1040, 520 and 430 cm(-1), along with the characteristic UV absorptions at 300 and 235 nm , were used for definitive assignment of the photochemical product. Th e proposed mechanism for the formation of Cl-(OClO) involves photolysi s of OClO to Cl + O-2 followed by migration of the Cl to a nonphotolyz ed OClO. While clustering of the OClO may play a role in the formation of the product, experimental evidence indicates that the OClO prefers to exists as a monomer solvated by the water. These results have pote ntial implications for stratospheric ozone loss: under the very dilute conditions that would exist on polar stratospheric ice particles, the photochemical conversion of OClO to Cl+O-2 would represent a new sour ce of Cl atoms for ozone depletion.