Vibrational analysis of oxygen adsorption on Cs and CO coadsorbate precovered Ru (0001) surface

Vibrational analysis of oxygen adsorption on the Cs and CO coadsorbate precovered Ru (0001) surface was carried out by means of high-resolution electron energy loss spectroscopy. For submonolayer Cs coverages on Ru (0001), an appropriate amount of CO adsorption leads to formation of (2 x 2)-Cs+2CO islands. Subsequent oxygen adsorption on this Cs and CO coadsorbate precovered surface results in a remarkable change of high resolution electron energy loss spectroscopy. The loss peak of C-O stretch mode for 2 x 2 island species decreases in intensity, which is accompanied by appearance of new bands at about 87 and 240 meV. The results show that Cs adatoms and CO molecules are rearranged upon oxygen adsorption, and are correlated with coexistence of bare surface CO and a mixed phase of Cs, CO, and O.