PHYSISORPTION OF CO AND N2 ON AL(111) - OBSERVATION OF SURFACE-MOLECULE VIBRATIONS IN ELECTRON RESONANCE SCATTERING

Monolayers of physisorbed CO and N2 on Al(111) were investigated by means of high-resolution electron-energy-loss spectroscopy (HREELS). The line shapes of the =01 molecular stretching modes differ largely. In the high-energy-loss tail of this mode, surface-molecule stretching losses are detected with an energy of 10.5 meV in the case of N2. It is demonstrated that this large inelastic intensity is due to the negative-ion resonance scattering mode operating for N2 but not for CO. The results are discussed in the framework of Gadzuks wave-packet method for time-dependent quantum behavior of molecules on surfaces. © 1990 The American Physical Society.