The adsorption of oxygen on Ag(110) at temperatures ranging from 300 to 500K was investigated by second-harmonic generation, low-energy electron diffraction and work function change measurements. For low oxygen doses the second-harmonic signal decreases in accord with the free electron model. Above ΘO=0.15 the second-harmonic intensity starts to increase, and at the saturation coverage ΘO=0.5 it reaches a level nearly 10 times that of the clean surface value. This enhancement was explained in terms of laser radiation field resonance with electronic transitions between bulk states and py-like surface states at the ¯Y-point of the surface Brillouin zone. This effect was most pronounced for p-polarized excitation. The results compare very favourably with band structure calculations assuming an oxygen-induced added-row reconstruction model.

Oxygen Chemisorption and Surface Reconstruction on Ag(110) Investigated with Second-Harmonic Generation. S.Reiff, J.H.Block: Surface Science, 1996, 345[3], 281-9