The dynamics of heterogeneous reactions at ice surfaces relevant to atmospheric, interstellar and hypergolic phenomena.

与大气、星际和自转现象相关的冰表面异质反应动力学。

• 批准号: RGPIN-2022-04602
• 负责人: Ayotte, Patrick
• 金额: $ 2.11万
• 依托单位: Université de Sherbrooke
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=748648
• 关键词: dynamics; heterogeneous; reactions; ice; surfaces

The investigations described in this proposal rely on the preparation of metastable species using molecular beam techniques to study interfacial chemical dynamics of key heterogeneous atmospheric, hypergolic, and interstellar chemistry reactions. The first theme will exploit a recently developed methodology to prepare trans-ONONO2, a metastable isomer of the nitrogen dioxide dimer that was proposed to be a key reaction intermediate for NO2 hydrolysis, but also for prototypical hypergolic reactions with hydrazine, H2NNH2. These important reactions will be investigated within amorphous solid water/hydrazine, and at their surface, at temperatures where reaction intermediates can be trapped and characterized spectroscopically by exploiting electric field standing waves (EFSW) to enhance the specificity and sensitivity of reflection-absorption IR spectroscopy (RAIRS) providing valuable molecular-level insight into reaction mechanisms and their dynamics. Custom instrumentation will also be developed to allow for these investigations to be performed under environmentally relevant conditions while field studies of the photochemical NOx fluxes at the Canadian High Arctic Research Station (CHARS) will also be initiated. The second theme aims at improving our understanding of confinement effects on the interconversion between ortho and para nuclear spin isomers (NSI) of small molecules (H2O, NH3, C2H2, and H2CO) for magnetic resonance applications in surface science. The proposed investigations build upon our unique capabilities for the preparation of beams of these small molecules enriched in their metastable ortho NSI using magnetic focusing thereby allowing state-to-state NSI interconversion dynamics upon scattering at surfaces to be performed by resonance-enhanced multi-photon ionization time-of-flight mass spectrometry (REMPI-TOF-MS). As confinement of NSI upon their adsorption at surfaces triggers their interconversion, the erosion of the enrichment in their ortho NSI hampers potential magnetic resonance applications to surface science relying on spin polarized molecules. Confinement effects will also be investigated in endofullerenes as recent work showed that the ro-translational dynamics could yield very slow erosion in the NSI distributions of D216O@C60 as the confinement-induced inter- and inter-molecular couplings responsible for NSI interconversion may be strongly suppressed in these compounds.  Materials with enhanced retention of their nuclear spin isomers are highly desirable and could find applications in magnetic resonance spectroscopy and imaging as well as quantum information processing.  These two research themes will provide ample opportunities for HQP to be trained in advanced custom experimental, numerical simulations, and molecular modelling methods of molecular sciences, in a highly collaborative environment, that involves industrial and academic partners from around the world.

本文所描述的研究依赖于利用分子束技术制备亚稳态物质来研究关键的非均相大气、自燃和星际化学反应的界面化学动力学。第一个主题将利用最近开发的方法制备反式onono2，这是二氧化氮二聚体的亚稳态异构体，被认为是NO2水解的关键反应中间体，也是与肼，H2NNH2的自沉反应的原型。这些重要的反应将在无定形固体水/肼中进行研究，并在它们的表面，在反应中间体可以被捕获的温度下进行研究，并通过利用电场驻波（EFSW）进行光谱表征，以提高反射-吸收红外光谱（RAIRS）的特异性和灵敏度，为反应机制及其动力学提供有价值的分子水平见解。还将开发定制仪器，以便在与环境有关的条件下进行这些调查，同时还将开始在加拿大高北极研究站（CHARS）对光化学NOx通量进行实地研究。第二个主题旨在提高我们对小分子（H2O, NH3， C2H2和H2CO）的邻位和对位核自旋异构体（NSI）相互转化的约束效应的理解，以用于磁共振在表面科学中的应用。所提出的研究建立在我们利用磁聚焦制备这些富含亚稳态邻位NSI的小分子光束的独特能力之上，从而允许通过共振增强的多光子电离飞行时间质谱（REMPI-TOF-MS）在表面散射时进行状态到状态的NSI相互转换动力学。由于NSI在表面上的吸附限制会触发它们的相互转化，因此其邻位NSI中富集的侵蚀阻碍了依赖自旋极化分子的表面科学的磁共振应用。约束效应也将在内富勒烯中进行研究，因为最近的研究表明，反平移动力学可能会对D216O@C60的NSI分布产生非常缓慢的侵蚀，因为在这些化合物中，负责NSI相互转化的约束诱导的分子间和分子间偶联可能被强烈抑制。具有增强核自旋同分异构体保留的材料是非常理想的，可以在磁共振波谱和成像以及量子信息处理中找到应用。这两个研究主题将为HQP提供充分的机会，在一个高度协作的环境中，与来自世界各地的工业和学术合作伙伴一起，在分子科学的先进定制实验、数值模拟和分子建模方法方面进行培训。