Electronic excited states of NO/Cu(111) studied by high-resolution two-photon photoelectron spectroscopy

A high-resolution two-photon photoelectron (2PPE) spectrometer was constructed and applied to NO adsorbed Cu(111). The apparatus was based on a high-repetitive tunable laser of picosecond pulse duration combined with a single-electron counting time-of-flight (TOF) system. Performance of the apparatus was examined with 2PPE spectra of Ag(111) and Cu(111) surfaces, Energy resolution better than 0.03 eV was achieved. A preliminary result for NO adsorbed Cu(111) surface showed that electronic states of adsorbed NO contain some fine structures, suggesting that the high-resolution 2PPE spectroscopy provides much information on electronic structure of adsorbed molecules.