In addition to beam-surface experiments, we have a second research component aimed at understanding the photochemical decomposition pathways that are important in stratospheric ozone depletion. Chlorine nitrate (ClONO2), for example, is an important reservoir species for chlorine and NOx in the stratosphere. By conducting a UV photodissociation study on ClONO2 in a molecular beam and detecting the photofragments with the rotatable mass spectrometer, we discovered that two dissociation channels occur with comparable probabilities: ClO + NO2 and Cl + NO3. The first of these dissociation pathways was previously believed to be unimportant. More recently, we completed a study of the UV photodissociation of the chlorine monoxide dimer, ClOOCl. Our experiments have demonstrated that photoexcitation of ClOOCl leads to dissociation via multiple pathways, producing ClO + ClO and 2Cl + O2. These results substantially confirm the long-held belief that ClOOCl photolysis is important in the catalytic destruction of ozone over the polar regions.

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