Introduction to quantitative data analysis in vibrational sum-frequency generation spectroscopy

Abstract

Analyzing molecules at aqueous interfaces in situ, in vitro, or even in vivo without the need for labels and/or disruptive sample preparation is crucial for the understanding and optimization of material’s interactions with its surrounding. In this context, a central theme is the ability to differentiate between molecules in the respective bulk phases and those that are located at the interface. Here we introduce vibrational sum-frequency generation (SFG) spectroscopy, a nonlinear optical technique that is capable to selectively probe molecules at interfaces. SFG spectroscopy can be applied under ex vacuo conditions and allows to record vibrational spectra from molecules at interfaces. Though this technique holds great potential in research themes involving aqueous interfaces, the data analysis of SFG spectra can get quite complex and often requires a comprehensive understanding of the underlying nonlinear optical processes. This chapter introduces experimental and theoretical aspects of SFG spectroscopy with a strong focus on data analysis. It is meant for scientists new to the field of SFG spectroscopy who like to explore its applicability and theoretical background or are starting to apply SFG spectroscopy in their own research.