Sum-frequency generation (SFG) spectroscopy is a powerful tool for not only identifying molecular species but also analyzing orientation configurations on a surface/interface. In this work we shall present formulation of the theoretical framework of electronic SFG spectroscopy, which signal could be greatly enhanced by tuning one or two incident beam frequencies resonant with electronic excited states. Simulated electronic SFG spectra resonant at the sum frequency of a pair of coumarin-derivative pH-indicator surfactant molecules, 4-methyl-7-hydroxycoumarin and its anionic counterpart (noted as MHC and MHC�), floating on the water surface were carried out and compared with experimental results as a demonstration. 

Theoretical formulation and computational simulation of electronic sum-frequency generation (ESFG) spectroscopy of surfactant on water surface

247th National Meeting (2014)

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