TIME-RESOLVED SURFACE KINETICS BY IR DIODE-LASER REFLECTION-ABSORPTION SPECTROSCOPY

An IR reflection-absorption technique using diode lasers as light sources was developed with a capability of mu-sec time resolution for studying surface kinetic processes. A polarization subtraction scheme was used to eliminate the absorption by species other than the adsorbate studied. The technique was first applied to the study of CO adsorption on, and thermal desorption from, a Cu(100) surface. On a timescale of one second, a 0.002 monolayer sensitivity was demonstrated. Absorption traces directly monitoring the CO concentration on the surface with real-time resolution at various frequencies near the CO stretching mode allow the in situ observation of adsorption and desorption. The observations suggest that there is more than one adsorption configuration for CO on Cu(100).