Second-harmonic generation and surface reconstruction: Cs on Ag(110)

The Cs induced reconstruction of the Ag(110) surface has been investigated by second-harmonic generation (SHG), combined with measurements of the work function change (Δφ) and thermal desorption spectroscopy (TDS). Adsorption of one monolayer of Cs at 100 K leads to a SHG amplification of 1100 compared to the signal level of the clean surface. Through annealing the sample, a local reconstruction can be obtained at temperatures between 165 and 220 K, as a precursor to the long range ordered (1 × 3) and (1 × 2) missing row reconstruction. The onset of the local reconstruction is identified by a sharp decline of the SH intensity. For θ _Cs < 0.24 this can be understood as a variation in the conditions for the resonance of the radiation field with optical transitions between Cs derived resonant levels, caused by a modified adsorption geometry.