Photoion recoil effect on photoelectron line as a probe of adsorbate–substrate interaction

Photoelectron ejected from a monolayer-on-substrate carries energy and momentum and results in local changes of atomic dynamics. The quasi-molecular recoil model is suggested to describe the characteristic spectral changes of the 1 s - 1 photoelectron line induced by the photoion recoil and to link the changes with chemical bonds between light atoms in monolayer and transition metals. Relationships between the changes and the potential function corresponding to the bonds are derived. Two cases of weak and strong covalent bonding are examined and discussed. It is shown that the photoion recoil effect on 1 s - 1 -photoelectron line provides a sensitive probe of adsorbate–substrate interaction.