IMAGE STATES AND LOCAL WORK FUNCTION FOR AG/PD(111)

Two-photon photoemission spectroscopy was employed for an investigation of the image states on Pd(111) with various coverages of Ag. Image states from areas with different thicknesses of the Ag layer can be observed simultaneously. This proves the applicability of the concept of a local work function. The decay length of the wave function of the image state on Ag(111) into the metal was determined experimentally to be 7.6 +/- 1.2 angstrom, and the probability to find the electron in the metal is estimated as 10%.