Simultaneous measurements of the light emission from excited neutral atoms sputtered by a 10 keV Kr** plus beam from Cu and Al surfaces and also the photoelectric emission current excited by a He-Ne laser have been made to study the effects on the excited atom yield caused by the deposition of a fractional monolayer of Cs and by the adsorption of O//2 on the cesiated surfaces. The presence of adsorbed Cs causes only a minor decrease in the yield of excited substrate particles, but significantly alters the dependence of the light emission intensity on the O//2 pressure from that observed on the clean substrates. The results suggest that the formation of individual metal-oxygen bonds at the surface leads to the chemical enhancement effect.