Alkali-metal-induced changes in the multielectron excitations of CO/Cu(100)

We have performed an ultraviolet-- and x-ray--photoemission-spectroscopy study of the changes in the main lines and satellite peaks in the core and valence regions of CO/Cu(100) when the CO is coadsorbed with K (submonolayer coverages of CTHETAK=0.3 and CTHETACO=0.3--0.4). The C 1s and O 1s core levels shift by {~}2 eV to lower binding energy relative to EF, and 5--6 eV relative to the vacuum in the promoted system. Reductions of 25--50 % in the relative intensities of all satellite peaks are observed in (CO+K)/Cu(100) versus CO/Cu(100). Little change occurs in the splitting of main line to satellite peaks between the two systems. We interpret these observations in terms of a recent model of alkali-metal promotion which involves CO 2{π} enhancement and strong direct CO 1{π}--K interaction and relate our results to current models of CO bonding and multielectronic excitations in chemisorbed systems.