Electron-Stimulated Reactions at the Interfaces of Amorphous Solid Water Films Driven by Long-Range Energy Transfer from the Bulk

The electron-stimulated production of D₂ from amorphous solid D₂O deposited on Pt(111) is investigated as a function of film thickness. The D₂ yield has two components that have distinct reaction kinetics. Using isotopically layered films of H₂O and D₂O demonstrates that the D₂ is produced in reactions that occur at both the Pt/amorphous solid water (ASW) interface and the ASW/vacuum interface, but not in the bulk. The energy for the reactions, however, is absorbed in the bulk of the films and electronic excitations diffuse to the interfaces where they drive the reactions.