SUBSTRATE MEDIATED SUPPRESSION OF POSTCOLLISION INTERACTION EFFECTS

The line shapes and kinetic energies of argon 2p(3/2) and 2P(1/2) phot oelectrons from monolayers adsorbed on a Ru(001) substrate were measur ed with an electron time-of-flight detector in the near-threshold regi on. Compared with gas phase results, the two main effects due to postc ollision interaction, i.e., line broadening and redshift of the kineti c energy of threshold electrons, are strongly suppressed on the surfac e. We show that these changes are brought about by an effective, scree ning induced reduction of the energy loss encountered by the threshold electron upon transition from a singly to a doubly charged central ar gon atom at core-hole decay. [S0031-9007(98)07162-2].