Soloviev, S.M.; Pettenkofer, C.; Pronin, I.I.; Pothekina, N.D.; Petrov, V.N.: Interaction of Pd electron states with adsorbed hydrogen. Surface Science 608 (2013), p. 165-172
10.1016/j.susc.2012.10.001
Abstract:
Investigations of electrons excited into image states (IS) of Pd clusters and their interaction with adsorbed 21 hydrogen using photoelectron (PE) spectroscopy with synchrotron radiation is presented. Pd clusters were 22 deposited on pyrolytic graphite surfaces which were used as inert substrates. PE spectra measured for Pd 23 clusters at low photon energies show additional peaks at energies of~4.7 and 5.25 eV that corresponds to 24 Pd image states at energies EIS 25 −Evac≈−0.75±0.1 eV and EIS−Evac≈−0.2±0.1 eV. After hydrogen adsorption on graphitewith Pd clusters the H-induced features: positive peaks at energy−2 eV, 26 −3.5 eV, −7 eV and a small negative peak at −4.6 eV, were observed in the valence band spectra of Pd below 27 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 28 −7 eV peak is due to strong interaction of Pd clusterswith hydrogen producing a H―Pd bonding adsorbate 29 state. 30 It is proposed that a charge transfer from IS2 to Pd-H bond dominates over the H 31 − anion neutralization via transfer of excess charge from H 32 − to IS1.