Quantum delocalization of H on Pd(110): A vibrational study

The vibrational spectra of H on Pd(110) at 90 K have been measured in the low-H-coverage region, by using high-resolution electron-energy-loss spectroscopy. Three dipole-active loss peaks associated with H adatoms were observed at 87--89, 96--100, and 121--122 meV. A model calculation based on the delocalization of H was made, which gives the energy positions and relative intensity variation of the two loss peaks in the range of 87--100 meV for different H coverages. There is a reasonable agreement between the calculated and experimental results. It is concluded that vibrationally excited H atoms on Pd(110) are described by the delocalized model. {} 1996 The American Physical Society.