PHOTOACOUSTIC DETECTION OF A SURFACE COMPLEX-INDUCED BY OPTICAL-ABSORPTION AT SILVER ELECTROLYTE INTERFACES

Photoacoustic (PA) signals generated at silver-electrolyte interfaces have been measured to investigate the charge-transfer (CT) transition effect in terms of the concentration change of a surface complex. At a silver surface with pyridine adsorbates, it is shown that the PA sign al produced by 514.5-nm radiation is directly related to the concentra tion of the surface complex in the nonfaradaic potential region while the signal by produced 1064-nm radiation is associated with the format ion and diffusion of surface adatoms in the faradaic region. As a cons equence, an irreversible loss of the surface-enhanced second-harmonic generation (SESHG) intensity has been observed because of the diffusio n of the surface complex, and this loss becomes profound with increasi ng excitation intensity and electrode potential. The experimental resu lts may provide a better insight into the physical mechanism for other surface-enhanced phenomena.