Far‐Ultraviolet Spectroscopy in the Solid and Liquid States, Principle, Instrumentation, and Application

Abstract

This article outlines the recent progress in ultraviolet ( UV ) spectroscopy in the 140–280 nm region of solid and liquid phases. In this article, we refer to the 120–200 nm region as the far ultraviolet ( FUV ) region. The word ‘vacuum UV region’ is not appropriate any more at least for the 120–200 nm region because a vacuum evaporation system is not always required, but a nitrogen gas‐purged system is often sufficient. FUV spectroscopy is concerned with electronic transitions of a molecule, but the absorptivity is very high in the FUV region, and therefore, this region has been employed to investigate mainly for the electronic states and structure of gas molecules. To observe the spectra of solid samples in the FUV region, reflection spectroscopy has been used. However, for liquid samples, in general, it is very difficult to use either absorption spectroscopy or reflection spectroscopy. Accordingly, FUV spectroscopy for liquid samples has almost been an undeveloped research area. To solve these difficulties in FUV spectroscopy, we have recently developed a totally new FUV spectrometer based on the attenuated total reflection ( ATR ) technique that enables us to measure the spectra of liquid and solid samples in the 140–280 nm region. This spectrometer has opened up a new era of FUV spectroscopy. This article consists of seven parts: (i) introduction to FUV spectroscopy, (ii) characteristics and advantages of FUV spectroscopy for the study of liquids and solids, (iii) development of new FUV spectrometers, (iv) FUV studies of liquid water and aqueous solutions, (v) FUV spectra of organic molecules in the liquid states, (vi) Classification of polymer thin films using FUV spectroscopy, (vii) FUV spectroscopy applied for photocatalysis, (viii) Structure of water adsorbed on an aluminum surface studied by variable angle‐ATR–FUV technique, and (ix) time‐resolved ( TR ) FUV spectroscopy. This article demonstrates that FUV holds considerable promise not only in basic science but also in applications such as qualitative and quantitative analyses, online monitoring, environmental geochemical analysis, and surface analysis.