THE EFFECT OF ATOMIC-SCALE SURFACE DISORDER ON BONDING AND ACTIVATION OF ADSORBATES - VIBRATIONAL PROPERTIES OF CO AND CO2 ON COPPER

Important details are resolved in the SERS spectra of CO and CO2 on disordered copper surfaces at 40 K. The spectrum of chemisorbed CO features four vibrational modes: a CO stretch vibration, a frustrated rotation and two frustrated translations, perpendicular and parallel to the local surface. The bands originate from a CO species singly coordinated to electron deficient defect sites, with the bond strength increased compared to non-defect adsorption. In the case of adsorbed CO2 two distinct adsorption states due to an activated and a non-activated surface species are observed. The activation is promoted by low temperature stabilized surface defects and is prohibited on an annealed copper surface.