Recent progress in the investigation of core hole-induced photon stimulated desorption from adsorbates: excitation site-dependent bond breaking, and charge rearrangement

We report photon stimulated desorption (PSD) of neutral and ionic molecules and atoms from CO chemisorbed on Ru(001) and Cu(111), and from N-2 chemiso rbed on Ru(001). Comparing branching ratios and spectral features for the O 1s and N1s regions, we demonstrate that desorbing neutrals and ions are sup plementary probes for the entire region of one- and multi-electron excitati ons, bearing valuable information on the transfer of energy and charge. For the primary [N1s]pi* excitation of N-2/Ru(001), we find excitation site-de pendent branching into desorption of N-2(0), N-0 and N+. PSD of neutral N a toms predominates for excitations of the N atom close to the surface, where as mainly neutral N-2 molecules and N+ ions are ejected for excitations of the outer N atom. At the Ru 3p substrate thresholds we find significant enh ancements of the N+ and N2+ yields from N-2/Ru(001), and discuss the electr onic nature of the underlying energy transfer mechanism. (C) 2000 Elsevier Science B.V. All rights reserved.