Surface resonances in a CH 4 monolayer physisorbed on a silver (111) surface

Abstract

Surface resonances in the scattering of low energy electrons with a physisorbed monolayer on a Ag(111) surface were studied with a high resolution electron energy loss spectrometer. The energy dependence of the intensity of elastic scattering (I–V curve) was measured on clean Ag(111), CH4 Ag(111), Xe Ag(111) and CH4 Xe Ag(111) at 40 K. The I–V curve from a CH4 Ag surface showed two dips at 3.7 and 4.0 eV which correspond to the threshold energy of surface wave excitation. The I–V curves for the inelastic scattering were measured via an energy loss process by the excitation of vibrational modes of CH4. As for the dipole active v4 mode, resonant features similar to those for the elastic peak, were observed while resonance effects against the dipole inactive v2 mode were poor.