Fundamental Studies of Heteorogeneous Procesess on Model Polar Stratospheric Cloud Surfaces

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This is a laboratory study of the chemistry of atmospheric trace gases in contact with solid surfaces, representative of the particulate matter of polar stratospheric clouds (PSCs). The solid matter will be ordinary water ice or frozen nitric acid trihydrate, which are believed to be constituents of the PSCs. Trace gases whose chemical reactions will be studied on the ice surfaces will be chlorine nitrate and nitrogen pentoxide. The ice solids will be studied both with and without dissolved impurities like hydrogen chloride, hydrogen bromide, and hydrogen fluoride. Solubilities of the impurities in the ices will be determined under a range of experimental conditions. The progress of chemical interactions between the gases and the solids will be followed by simultaneous mass spectroscopy of the gases and by infrared spectroscopy of the solids. This will allow real-time observations of the mutual interactions of the gases and the ice solids. Water ice and frozen nitric acid trihydrate in the polar stratospheric clouds are believed to act as catalysts for chemical reactions of chlorine- and nitrogen-containing gases involved in ozone depletion in the stratosphere. These laboratory studies will develop new information about detailed chemical and physical mechanisms of transformations of chlorine and nitrogen compounds in the stratospheric ozone layer. Such information will help to confirm (or modify?) present beliefs about ozone depletion in the stratosphere and will help us understand the timing of ozone depletion and its relationships to geographic factors.