Surface and image-potential states on Pt(111) probed by two- and three-photon photoemission

The surface state and image-potential state (IPS) on Pt(111) have been studied by multi-photon photoemission spectroscopy. The intensity of two-photon photoemission by nanosecond laser pulses shows a resonant transition from the sp-derived surface state to the n = 1 IPS at 5.39 ± 0.03 eV. The three-photon photoelectron spectrum by femtosecond pulses shows two peaks: photoemission from the n = 1 IPS populated by nonresonant transitions and that from the surface state. The surface state is located at 0.19 ± 0.05 eV below the Fermi level and the n = 1 IPS at 0.78 ± 0.05 eV below the vacuum level.