Resonant soft-x-ray emission spectroscopy of surface adsorbates: Theory, computations, and measurements of ethylene and benzene on Cu(110)

Soft-x-ray emission spectra from C2H4/Cu(110) and C6H6/Cu(110) have been ob tained for two excitation energies, resonant and nonresonant, and resolved in all three spatial components (x,y,z). The one-step theory for resonant s oft x-ray spectroscopy and Raman scattering is extended to adsorbates on me tal surfaces and is implemented within a density-functional theory framewor k. The calculations are performed for ethylene and benzene chemisorbed on C u(110) using cluster models (up to 86 Cu atoms) of the metal surface; the c alculations are performed for both resonant and nonresonant excitation with the focus on the polarization and symmetry selectivity and the role of cha nnel interference. The molecular mirror plane symmetry is maintained for th e chemisorbed system, and for the generated con hole, which leads to an ene rgy-dependent symmetry and polarization selectivity in the emission process . The calculations and experiment show good agreement both with regard to i ntensities and energy positions of the peaks. [S0163-1829(99)05804-X].