Electrochemical and spectroelectrochemical data indicate that underpotentially deposited silver adatoms on gold substrates are photolyzed to form silver metal clusters. The surface gold-gold stretch and gold-silver stretch bands are observed, as well as the surface chloride complex stretch. The chloride complex interacts with ions in the solution phase, giving rise to shifts in the metal-chloride stretching vibrational frequency as a function of the applied electrode potential. The metal-metal bands are independent of the electric field at the electrode surface. The origin of these bands is discussed.