Interaction of Pd electron states with adsorbed hydrogen

Investigations of electrons excited into image states (IS) of Pd clusters and their interaction with adsorbed hydrogen using photoelectron (PE) spectroscopy with synchrotron radiation is presented. Pd clusters were deposited on pyrolytic graphite surfaces which were used as inert substrates. PE spectra measured for Pd clusters at low photon energies show additional peaks at energies of ~ 4.7 and 5.25 eV that corresponds to Pd image states at energies EIS − Evac ≈ − 0.75 ± 0.1 eV and EIS − Evac ≈ − 0.2 ± 0.1 eV. hydrogen adsorption on graphite with Pd clusters the H-induced features: positive peaks at energy − 2 eV, − 3.5 eV, − 7 eV and a small negative peak at − 4.6 eV, were observed in the valence band spectra of Pd below EF. While the peaks at − 3.5 eV and − 2 eV are the result of the formation of H-induced states in the SBZ the − 7 eV peak is due to strong interaction of Pd clusters with hydrogen producing a H―Pd bonding adsorbate state. proposed that a charge transfer from IS2 to Pd-H bond dominates over the H− anion neutralization via transfer of excess charge from H− to IS1.