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

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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.