Room-Temperature in Vacuo Chemisorption of Xenon Atoms on Ru(0001) under Interface Confinement

Molecules confined at the nanoscale can exhibit intriguing physical and chemical properties. We report here the direct observation of room-temperature in vacuo chemisorption of xenon (Xe) atoms on Ru(0001) under spatial confinement. Weakly bound two-dimensional (2D) silica bilayer films consisting of hexagonal prisms (∼0.5 nm) were synthesized on a Ru(0001) substrate. The distance between the 2D silica and the Ru(0001) surface can be controlled by changing the coverage of oxygen chemisorbed on Ru(0001), creating an interfacial space of tunable sub-nanometer thickness. Individual Xe atoms are trapped at 300 K in this nanosized volume. Combined in situ synchrotron-based X-ray photoelectron spectroscopy (XPS) and density functional theory studies reveal that the hybridization between Xe and Ru orbitals leads to the formation of a Xe-Ru bond with a significant amount of charge transfer, which can explain the observed core-level binding energy shifts in the XPS measurements. This work opens exciting opportunities to study the chemistry of individual noble gas atoms under extreme confinement.