Investigation CO Adsorption on Cs/Ru(10(1)over-bar0) Surface Using ARUPS

CO adsorption on Ru(10 (1) over bar0) and Cs/Ru(10 (1) over bar0) surfaces has been investigated using ARUPS, at low temperature 150K. The 5 sigma+1 pi and 4s levels of CO molecule were found in angle-rcsolved UP spectra showing that CO is in molecular adsorption states on clean and Cs precovercd Ru(10 (1) over bar0). The dependence of CO 4 sigma intensity on incident angle suggests that adsorbed CO stands upright on clean Ru(10 (1) over bar0) surface; But adsorbed CO, with a short-range interaction with Cs atom [(15)], does not stand upright and tilts in <1<(2)over bar>10> azimuth on a Cs-precovered Ru(10 (1) over bar0) surface.