Observation of neutral atomic fragments for specific 1s core excitations of an adsorbed molecule

We have succeeded in detecting a neutral atomic fragment produced by energy- and polarization-specific molecular core electron excitations, enabling a comparison of oxygen atom and oxygen ion yields from photon induced dissociation of chemisorbed CO molecules on the Ru(001) surface. Resonances in the O⁰ atom yield are observed at 534 and 550eV, but no enhancement is observed for higher-energy excitations which stepwise increase the O⁺ yield. The mechanistic reasons for the similarities and differences in neutral and ionic fragment production are discussed, with emphasis on the influences of charge transfer and redistribution processes.