High-resolution X-ray absorption spectra of the pi* resonance of N-2 directly physisorbed on Cu(100)

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