Development of Heterodyne-Detected Total Internal Reflection Vibrational Sum Frequency Generation Spectroscopy and Its Application to CaF2/Liquid Interfaces

摘要

We present heterodyne-detected total internal reflection vibrational sum frequency generation (HD-TIR VSFG) spectroscopy for CaF2/liquid interfaces. With this technique, absolute orientations at solid/liquid interfaces can be determined by measuring complex chi((2)) spectra of the buried interfaces. We applied the technique to CaF2/sodium dodecyl sulfate (SDS) solution interfaces, and directly determined the polar orientations of the water molecules and surfactants at the interface based on the phase information on VSFG spectra, which is unavailable in conventional homodyne-detected TIR VSFG spectroscopy. The reorientation of the interfacial water molecules was observed as a change of the sign of Im[chi((2))] depending on the surfactant concentration.