Theoretical study of the valence level photoemission spectrum of C2H2 adsorbed on a Ni metal surface

Abstract

In order to investigate the valence-level photoemission spectrum of C 2 H 4 adsorbed on a Ni metal surface, we calculated the valence-hole spectral functions of NiC 2 H 4 ͑ bonding͒ using the ab initio third-order algebraicdiagrammatic-construction "ADC͑3͒… Green-function method using an extended basis set. We obtained an overall good agreement with experiment. The changes in the spectral features such as the changes in the separations of the ionization energies from the gas phase to the chemisorbed phase are due to the metal ligand bonding exerted via the charge-transfer excitations and do not arise from the distortion of the molecule, which occurs upon chemisorption. ͓S0163-1829͑97͒01004-7͔