Investigation of the electronic states of materials with attenuated total reflection in the far-ultraviolet region

We have developed an attenuated total reflectance spectrometer in the FUV region (ATR-FUV) and pioneered a technology to easily observe FUV spectra in solutions. Due to its simplicity, feasibility and reproducibility, ATR-FUV has allowed us to observe and report on a wide variety of liquid and solutions. Moreover, significant progress in quantum chemical calculations for electronic excitation states of molecules improves our interpretations of the FUV spectra. In the series of studies, we investigated the FUV region of various molecules by ATR-FUV spectroscopy, namely, organic molecules, water, and aqueous solutions of biomolecules. For example, it was revealed that the first electronic transition of water in the FUV spectrum changes very sensitively depending on the coordination experienced by the lone pair electron of water. The ATR-FUV spectra of super concentrated aqueous solutions, such as Water-in-Salt (WIS) and Hydrated Melt (HM) using a lithium salt, were investigated. Additionally, transitions from σ electrons, which form the backbone of organic compounds, are also observed. We will also introduce research on hyperconjugation of the σ electron orbit through observation of these transitions.