Validation of Spectra and Phase in Sub-1 cm–1 Resolution Sum-Frequency Generation Vibrational Spectroscopy through Internal Heterodyne Phase-Resolved Measurement

• DOI: 10.1021/acs.jpcb.5b07780
• Publication Date: 2015-10-28T15:23:54Z
• Authors: Li Fu; Shun-Li Chen; Hong-Fei Wang
• Keywords: Spectral resolution

Reliable determination of the spectral features and their phases in sum-frequency generation vibrational spectroscopy (SFG-VS) for surfaces with closely overlapping peaks has been a standing issue. Here we present two approaches toward resolving such The first utilizes high-resolution accurate line shape from recently developed subwavenumber broadband SFG-VS (HR-BB-SFG-VS), which detail parameters, including relative phases, can be determined through reliable fitting. These results are further validated by using second method that azimuthal angle phase dependence z-cut α-quartz crystal, common standard, interference between SFG fields quartz surface, as internal reference, adsorbed molecular layer. Even though this approach is limited to layers transferred or deposited onto it simple straightforward, requires only an standard single measurement free drifts. More importantly, provides unambiguous information on surfaces. Using method, absolute susceptibility tensors CH3, CH2, chiral C–H groups different Langmuir–Blodgett (LB) monolayers drop-cast peptide films determined. fully consistent complement each other, making both easily applicable tools studies. because HR-BB-SFG-VS technique applied various interfaces, validation demonstrates one most promising interrogating detailed structure interactions complex interfaces.