RAMAN-SCATTERING FROM CARBON-MONOXIDE ADSORBED ON EVAPORATED SILVER FILMS

We present an ultrahigh vacuum study of the carbon monoxide-silver system using Raman scattering. Silver films deposited in UHV on a room-temperature substrate cooled close to 78 K and exposed to saturation doses of CO show Raman lines at 1995 and 2070 cm** minus **1. These disappear upon warming to room temperture. Films freshly deposited on a cooled substrate show a line at 2010 cm** minus **1 which appears at 10 L and grows in intensity through 10**5 L. A second line, thought to be due to residual CO, is visible on the fresh film at 2124 cm** minus **1 and shows only minor changes with CO exposure. Further study of surfaces prepared in this manner shows at least 16 lines in the region 40-2600 cm** minus **1 after exposure to 10**5 L of CO. Analysis of the data shows the utility of Raman scattering as a surface probe.