Theory and Applications of Sum-Frequency Generations

The SFG technique has become popular since the pioneering work conducted by Shen's group in late 1980s. Combined the advantages of other surface‐detecting techniques, the SFG technique could identify both chemical species and orientations adsorbed on surfaces or inserted between surfaces. In view of the recent tremendous experimental activities of SFG in surface chemistry, biochemistry and material sciences, quantum chemical calculations of SFG spectra to analyze the experimental SFG spectra are badly needed. In this paper we presented the theoretical expressions of various SFG techniques and showed how to employ the quantum chemical calculations to simulate the corresponding SFG spectra. We presented the theoretical expressions of various SFG techniques (resonance—off‐resonance, off‐resonance—resonance, and resonance—resonance cases) and showed how to employ the quantum chemical calculations to simulate the corresponding SFG spectra.