On-Surface Dynamics Visualized via Supersonic Molecular Beam Scattering and Scanning Tunneling Microscopy

On-surface reaction dynamics play a critical role in chemical processes ranging from heterogeneous catalysis to the fabrication of semiconductors for electronic devices. Research presented in this thesis interrogates interfacial dynamics with angstrom-level resolution using an in situ scanning tunneling microscope in line with a supersonic molecular beam. A triply differentially pumped molecular beam line provides angle- and energy-selected gas molecules to access at times highly activated surface chemistry such as the dissociative adsorption of nitrogen on Ru(0001). Tight control of incident molecular kinetic energy and impinging angle paired with the ability to visualize the on-surface products of single molecule dissociation events provides previously unattainable insight into the energy dissipation channels governing reactivity in the N2/Ru(0001) system. Results demonstrate long-ranged non-thermal motion of N atoms following dissociation over a range of incident impact conditions. Next, nanolithography using a field emitting probe to dissociate CH species and localize oxygen atoms is revealed, promising the creation of nanopatterned 2D devices, quantum sensors, or next-generation catalysts using surface species as "atomic ink." Growing graphene across the Ru(0001) surface produces a moiré patterned interface, and scattering ground state atomic oxygen reveals the role spin-flipping dynamics play in reactivity across monolayer versus bilayer graphene. Site-specificity and diffusivity of atomic oxygen on the moiré is shown to be coverage dependent with multiparticle interactions leading to correlated surface diffusion and higher surface mobility. The role of multiparticle interactions is again emphasized through co-deposition of buckminsterfullerene and atomic oxygen on moiré patterned graphene lending insight to thin film growth. Overall, results demonstrate a new direction in molecular scattering in which tight control of incident molecular kinematics is coupled with atomically resolved microscopy to probe on-surface dynamics.