We are using a unique combination of supersonic and thermal molecular beams in conjunction with in situ scanning tunneling and atomic force microscopy to elucidate spatial-temporal correlations in interfacial reactivity.  For example, time-lapse visualization of reacting interfaces is allowing us to probe the reactivity of specific sites at complex interfaces and how the presence of a reacted site or local region influences the subsequent reaction probability at proximal sites.  Such correlations are important in chemisorption, catalysis, materials oxidation and erosion, and film processing.  This capability also opens up a new view for interfacial reaction dynamics where incident beam kinetic energy and angle of incidence can be used for reaction control parameters with outcomes such as site-specific reactivity, overall time-evolving mechanisms, and where the on-surface fate of chemisorbed species can be definitively ascertained.  These experiments are being carried out in arguably unique UHV gas-surface scattering instruments where the time-evolving interface can be probed either in real-time or, for reactions occurring under extreme thermal conditions, using time-lapse sequential imagery.  Illustrative examples include the oxidation of Si(111)-(7x7), the oxidative erosion of HOPG graphite, and a large family of self-assembled monolayers reacting with energetic species such as atomic hydrogen.  Other topics that may be covered include methodologies for assessing the relative importance of adiabatic and non-adiabatic interactions in chemisorption phenomena, as well as our approach for examining geometry-restricted interfacial reaction dynamics.  Such measurements as noted above provide an incisive and informative complement to traditional gas-surface scattering measurements where product production and energy disposal are typically obtained, with surface visualization now adding the ability to correlate time-evolving morphological changes with time-evolving mechanistic pathways and overall kinetics.

Spatio-temporal reaction kinetics at interfaces

2019 Spring National Meeting

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.