High-resolution X-ray absorption spectra of the π* resonance of N2 directly physisorbed on Cu(100)

High-resolution NEXAFS spectra of the pi* resonance of N-2 molecules directly physisorbed on a Cu(100) surface are reported. The vibrational fine structure of this resonance, even for very low coverages, could be resolved, allowing the performance of a vibrational analysis of the experimental spectra. We obtain changes in the vibrational properties of the physisorbed molecules compared to those in the gas phase. This is due to the direct adsorbate-substrate interaction for N-2 coverages up to 1 ML and to the adsorbate-adsorbate interaction for the multilaver. (C) 2001 Elsevier Science B.V. All rights reserved.