Surface Enhanced Raman Scattering of CO Adsorbed on Silver Film

抄録

We have observed the surface enhanced Raman scattering on the CO molecules adsorbed on the silver films which were prepared in the ultra high vacuum at 15 K. The molecules chemically adsorb below 120 K. Three intense Raman bands were found to grow at 155, 180 and 2142 cm⁻¹. With increasing the thickness of the CO overlayer on the silver surface, the peak of the stretching band at 2142 cm⁻¹ shifts to the low energy side, and the intensity and the band width increase. This result clarifies large discrepancies among reported values of the peak and the band width by other researchers. Rare gas atoms of Kr and Xe overlaid on the CO molecules have been found to induce similar coverage dependence to that observed in the case of the CO overlayer. Therefore, the dipole-dipole interaction is not a main cause of the coverage dependence. Chemical effect is considered to be a possible cause.