Time-Resolved Surface Dynamics: Directed Reactivity, Extraterrestrial Ices, and Nerve Agent Simulants

Abstract

This thesis describes a diverse cross-section of interfacial surface chemistry, ranging from investigating controlling reaction dynamics with an ordered surface, to modifying extraterrestrial ice, to destroying chemical warfare agents. In an update to the days of oriented, crossed molecular beam experiments, self-assembled monolayers of thiolates on gold were used as a participant in an O(3P) addition reaction, showing that restricting collisions to mainly unfavorable mutual orientation produces a low reaction probability despite sufficient energetics. The use of the ordered monolayer aids in rapid dissipation of collision energy, leaving intermediates that would normally rip apart in the gas phase. It has also been shown that neutral gaseous projectiles traveling with large momentum can directly embed into amorphous water ice, remaining trapped until the ice can desorb. This discovery, novel in the case of neutral projectiles, better informs modeling growth of astrophysical bodies and aircraft icing. Finally, the destruction by O(3P) of a pair of condensed-phase films of compounds simulating the G-series chemical warfare agents was studied, showing the close proximity afforded to intermediates resulted in formation of polymeric overlayers that exhibit greater thermal stability than the original simulants. These overlayers restrict the rate of destruction as they form. These experiments highlight the efficacy and wide applicability of time-resolved reflection-absorption infrared spectroscopy of surfaces during exposure to streams of atoms and molecules of tunable energy and flux.