Interfacial specificity of heterogeneous atmospheric and interstellar chemistry on ice/Spécificité interfaciale de la chimie atmosphérique et interstellaire sur la glace

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Our research program provides quantitative molecular-level descriptions of elementary heterogeneous processes on ice in order to improve our description of poorly understood atmospheric chemistry and astrophysical phenomena involving ice surfaces. Our approach relies on a combination of molecular beam and surface chemistry techniques, in concert with optical and electronic spectroscopy and microscopy, to study the complex coupled kinetics for adsorption, desorption and reaction of impurities onto thin ice films, as well as their absorption and diffusion within the bulk. Through molecular modelling and simulations, we provide detailed descriptions of how interfacial (photo)chemical processes differ from their bulk analogues using laboratory model systems inspired from atmospheric chemistry problems. The proposed work will improve our fundamental understanding of how simple acid molecules (HF, HCl, HBr, HNO3) adsorb onto ice, how they dissolve and become absorbed into ice, important elementary processes in atmospheric chemistry phenomena such as stratopheric ozone depletion. We also intend to consolidate recent and ongoing investigations of heterogeneous nitrates photochemistry in an attempt to better understand the source of the intense photochemical NOx fluxes observed to emanate from the snowpack to the polar boundary layer upon polar sunrise. Finally, recent developments in the separation of spin isotopomers of water poises us to undertake the development of an exciting new direction: studies of spin conversion chemistry of water in matrices and ice as well as its homogeneous and heterogeneous catalysis. This classical chemical physics problem promises to teach us how ortho-para ratios measured in the interstellar medium, such as those of water molecules sublimating from comets, are related to the temperature of the ice and also, of the primordial nebulae. It will also help establish experimental protocol for the preparation and storage of highly enriched samples of o-H2O and p-H2O for the study of how spin chemistry maps from reactants to products in chemical reactions involving indiscernible protons.