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

我们的研究项目提供了对冰上基本非均质过程的定量分子水平描述，以改善我们对涉及冰表面的大气化学和天体物理现象的描述。我们的方法依赖于分子束和表面化学技术的结合，与光学和电子光谱和显微镜相结合，研究杂质在薄冰膜上的吸附、解吸和反应的复杂耦合动力学，以及它们在体中的吸收和扩散。通过分子建模和模拟，我们使用受大气化学问题启发的实验室模型系统，详细描述了界面（光）化学过程与它们的体类似物的区别。这项工作将提高我们对简单酸分子（HF, HCl, HBr, HNO3）如何吸附到冰上，它们如何溶解并被冰吸收，以及大气化学现象（如平流层臭氧消耗）中重要的基本过程的基本理解。我们还打算巩固最近和正在进行的非均质硝酸盐光化学研究，以便更好地了解在极地日出时观测到的从积雪向极地边界层散发的强烈光化学NOx通量的来源。最后，在水的自旋同位素分离方面的最新进展使我们能够着手发展一个令人兴奋的新方向：研究水在基质和冰中的自旋转化化学及其均相和多相催化作用。这个经典的化学物理问题有望告诉我们，在星际介质中测量的对视差比，比如从彗星中升华出来的水分子的对视差比，是如何与冰的温度以及原始星云的温度联系起来的。它还将有助于建立制备和储存高富集o-H2O和p-H2O样品的实验方案，用于研究在涉及不可见质子的化学反应中，自旋化学如何从反应物映射到产物。

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.