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. Author manuscript; available in PMC: 2019 Jun 1.
Published in final edited form as: Top Catal. 2018 Apr 17;61(9-11):1101–1124. doi: 10.1007/s11244-018-0924-3

Figure 9.

Figure 9

a) A setup for PS-SFG. A concave mirror ensures that the Vis, IR and SFG beams from the sample are refocused onto the LO and that the SFG signal and the LO signal are collinear. The silica plate induces a delay of 1.7 ps between SFG and LO signals. b and c) A frequency domain interferogram is obtained, which can be Fourier transformed into the time domain where one of the interference terms (in this case at +1.7 ps) can be selected by filtering. d) Transforming back to the frequency domain yields the real (solid) and imaginary (dashed) interferograms. Division of the sample signals by the nonresonant reference yields the clean spectra. e and f) The real and imaginary parts of the water vibrations flip in sign relative the CHX stretches when switching from SDS to CTAB surfactants at liquid/air interfaces as the head-group charge induces different water orientations. Reprinted with permission from ref. [115], copyright 2009 American Institute of Physics Publishing.