Spiers Memorial Lecture: the dynamics of elementary reactions

Publisher Website
Google Scholar
Abstract
Comparing the reaction F + Na2→ NaF + Na(i)(where i are electronically excited states) in the thermal and hyperthermal regimes one sees evidence of a transition from near-statistical to a deterministic regime; the increased collision energy has narrowed the range of intermediate configurations. Ordering can be achieved more precisely by photoinducing reaction in an aligned condition, either in a van der Waals cluster (Wittig et al.) or in surface-aligned photoreaction. Both methods are reviewed. In the latter case the alignment can be demonstrated by studying photofragment angular distributions. The surface can enhance the photodissociation cross-section by 103–104 times. Theory indicates that reaction product angular distribution relative to the surface will be sensitive to the geometry of reactant adsorption. Photodetachment from surfaces could be used in a crossed ablated beam (CAB) variant of the crossed molecular-beam approach, employing beams which are purely free radicals, or (by ‘photoejection’) accelerated molecules. An adsorbate-covered surface with rectangular grooves that align photoreagents would constitute a ‘morphological catalyst’. We note pitfalls and progress in the realm of transition-state spectroscopy. Emission from sodium iodide vapour in the process of photodissociation, i.e. in an unbound ‘transition state’ NaI+, is obscured by the small fraction of NaI* that is present in a shallow bound state. For the case of H + D2→ HD + D it has proved possible to detect HD2 [graphic omitted] in the transition state by two-photon ionization.

This publication has 0 references indexed in Scilit: