PREFERENTIAL BONDING ORIENTATIONS OF FERROCENE ON SURFACES

We have measured the molecular orientation and bonding of adsorbed fer rocene on Ag(100) and Cu(100) using angle-resolved photoemission spect roscopy (ARPES). The results for molecular adsorption on Ag(100) are c omplemented by high-resolution electron energy loss spectroscopy (HREE LS) measurements and ab initio calculations for the ferrocene vibratio nal modes. The measurements indicate that ferrocene adsorbs on Ag(100) with the molecular axis perpendicular to the surface. In contrast, as indicted using ARPES and scanning tunneling microscopy, ferrocene ads orbed on the Cu(100) surface is oriented with the molecular axis paral lel with the surface. Model calculations allow us to assign all of the observed vibrational modes for the weakly bound molecular ferrocene o n Ag(100)-both dipole and impact scattering modes have been observed.