Off-specular and out-of-plane vibrational electron energy loss spectra of benzene and pyridine adsorbed on Pt(110)

The VEEL spectra of benzene, deuterobenzene, and pyridine adsorbed on Pt(110) at room temperature have been examined in emission planes both coincident with and orthogonal to the plane of incidence. The inelastic peak intensities are found to be almost independent of angle in both directions. This implies that neither of the established mechanisms, nor others presently examined, is an adequate description of the scattering. It also leads to a reassignment of the benzene spectrum.