VIBRATIONAL DYNAMICS OF CO AT THE (100)PLATINUM ELECTROCHEMICAL INTERFACE

The vibrational relaxation of the CO stretching vibration when the mol ecule is adsorbed at a (100) platinum single crystal electrode in aque ous electrolyte is investigated by sum-frequency generation, The measu red vibration lifetime of 1.5 +/- 0.5 ps is in line with those previou sly observed for dry CO/metal interfaces. No lifetime modification upo n electrode potential shift of 0.5 V could be detected. Consequently, the electrolyte or the interfacial electric field has little effect on the fast vibrational dynamics resulting from the non-adiabatic coupli ng of the vibration to the substrate electrons. It is speculated that the observation of a significant lifetime modification upon electrode potential shift would require non-aqueous electrolytes where the CO/Pt interface can be stable over a larger potential range.