We have measured the molecular orientation and bonding of adsorbed ferrocene on Ag(100) and Cu(100) using angle-resolved photoemission spectroscopy (ARPES). The results for molecular adsorption on Ag(100) are complemented by high-resolution electron energy loss spectroscopy (HREELS) measurments and ab initio calculations for the ferrocene vibrational modes. The measurements indicate that ferrocene adsorbs on Ag(100) with the molecular axis perpendicular to the surface. In contrast, as indicated using ARPES and scanning tunneling microscopy, ferrocene adsorbed on the Cu(100) surface is oriented with the molecular axis parallel with the surface. Model calculations allow us to assign all of the observed vibrational modes for the weakly bound molecular ferrocene on Ag(100)-both dipole and impact scattering modes have been observed.

Single crystal MnO͑100͒ substrates can be selectively oxidized to produce Mn 2 O 3 -and Mn 3 O 4 -like surfaces under mild oxidation/reduction conditions readily accessed under ultrahigh vacuum ͑UHV͒. MnO͑100͒ yields a characteristic Mn 2p x-ray photoelectron spectroscopy ͑XPS͒ satellite structure and appropriate O/Mn concentrations from O 1s/Mn 2p XPS intensity ratios. Its high resolution electron energy loss ͑HREEL͒ spectrum shows a series of Fuchs-Kliewer multiple phonon excitations with a single loss energy of 70.9 meV, characteristic of the cubic manganese monoxide structure. However, the HREEL spectral ͑HREELS͒ background is high and the phonons are not as well resolved as those typically observed on comparable metal monoxides. Annealing the MnO͑100͒ substrate at 625 K and 5ϫ10 Ϫ7 Torr O 2 slowly forms Mn 2 O 3 , as indicated by O 1s and Mn 2p XPS, and does so without significantly altering the symmetry of the MnO͑100͒ low energy electron diffraction pattern. The MnO͑100͒-Mn 2 O 3 surface can be selectively reduced to Mn 3 O 4 -like composition by heating under UHV to 775 K and to MnO͑100͒ at 1000 K. HREEL spectra for the UHV annealed surfaces are well-resolved, and for the MnO͑100͒-Mn 3 O 4 substrate a second fundamental phonon loss is observed at 55.6 meV as a result of the lower symmetry of the Mn 3 O 4 spinel structure. The UHV-annealed MnO͑100͒ surface appears to be more highly ordered since its HREELS phonon loss peaks are better resolved. It is also somewhat reduced, however, resulting in a less intense phonon spectrum with a fundamental loss energy of only 65.1 meV.

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