Depth profiling of water molecules at the liquid-liquid interface using a combined surface vibrational spectroscopy and molecular dynamics approach.

The studies presented here combine experimental and computational approaches to provide new insights into how water structures and penetrates into the organic phase at two different liquid-liquid systems: the interfaces of carbon tetrachloride-water (CCl4-H2O) and 1,2-dichloroethane-water (DCE-H2O). In particular, molecular dynamics simulations are performed to generate computational spectral intensities of the CCl4-H2O and DCE-H2O interfaces that are directly comparable with experimental measurements. These simulations are then applied toward the generation of spectral profiles, responses that vary as functions of both frequency and interfacial depth.

Understanding the population, coordination, and orientation of water species contributing to the nonlinear optical spectroscopy of the vapor-water interface through molecular dynamics simulations.

Molecular dynamics simulations are used to deconvolve the vibrational spectral features of the vapor-water interface based on molecular environment. A simple geometric description of hydrogen bonding is deployed to identify the OH stretch modes that comprise the vibrational sum-frequency spectrum of the vapor-water interface with direct comparison to our experimental results. The population densities of different species of water molecules are presented as functions of interfacial depth and orientation.