Effects of third-order susceptibility in sum frequency generation spectra: a molecular dynamics study in liquid water. Issue 5 (13th June 2017)

• Record Type: Journal Article
• Authors: Joutsuka, Tatsuya; Hirano, Tomonori; Sprik, Michiel; Morita, Akihiro
• Is Part Of: Physical chemistry chemical physics. Volume 20:Issue 5(2018)
• Page Start: 3040
• Page End: 3053
• Publication Date: 2017-06-13
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/c7cp01978e
• Languages: English
• ISSNs: 1463-9076

Abstract

Abstract : χ (2) and χ (3) at charged interfaces in SFG spectroscopy are distinctively calculated using MD simulations. Abstract : When sum frequency generation (SFG) spectroscopy is applied to charged solid/liquid interfaces, the observed SFG signals include both the second-order and third-order polarizations. The latter is called the χ (3) effect, which mainly includes induced molecular orientation by electric fields at charged interfaces. We theoretically evaluate the χ (3) effect on the SFG spectroscopy of liquid water using molecular dynamics (MD) simulations. The MD simulations enable us to definitely calculate the χ (3) susceptibility as a bulk property, and thereby separating it from the usual χ (2) effect shown in the SFG spectra. The calculated results of χ (3) for liquid water are fairly consistent with the experimental estimates. The present finding is utilized to analyze the spectral change of SFG at the air/water interface under electric fields and at the charged silica/water interface. The present analysis of the spectral changes allows for distinguishing the intrinsic change of the interface structure and the χ (3) effect from bulk liquid.