Fig. 2. (a) Energy level diagram in a VSFG process. The IR pulse creates a vibrational coherence between v = 0 and v = 1 states, which, in turn, gets upconverted by the visible pulse. The SFG signal is emitted in the phase matching direction with its frequency equal to the sum of the frequencies of the two input pulses. (b) A representative VSFG spectra of the nitrile-stretch of 4-mercaptobenzonitrile (4-MBN) on gold as a function of potential, adapted from a publication by Sarkar et al.63 (c) The electrochemical VSFG set-up used in the Lian lab. Figures (a) and (c) are adapted from a publication by Ge et al.64.
