Substrate Mediated Suppression of Postcollision Interaction Effects

The line shapes and kinetic energies of argon 2p3/2 and 2p1/2 photoelectrons from monolayers adsorbed on a Ru(001) substrate were measured with an electron time-of-flight detector in the near-threshold region. Compared with gas phase results, the two main effects due to postcollision interaction, i.e., line broadening and redshift of the kinetic energy of threshold electrons, are strongly suppressed on the surface. We show that these changes are brought about by an effective, screening induced reduction of the energy loss encountered by the threshold electron upon transition from a singly to a doubly charged central argon atom at core-hole decay.