Developments of a Liquid Flow Cell for Soft x-ray Spectroscopy and Observations of Water Molecules in Liquid Solutions

Soft x-ray spectroscopies which utilize electronic transition of core electrons are known as a powerful tool for observing electronic structures, and are extensively applied to solid and gaseous samples in vacuum. While soft x-ray requires a vacuum because of its low penetration ability, one cannot hold liquid phase samples in vacuum due to the vaporization of liquids. Therefore, soft x-ray measurement of liquid samples was one of the difficult experiments only a decade ago. Recently, extensive developments in experimental techniques have enabled the application of x-ray emission and absorption spectroscopy to liquid and solution samples. In this article, our recent investigations on electronic state concerning liquid structure of water using soft x-ray beamline BL17SU in third generation synchrotron facility SPring-8 are reviewed. In addition, the development of experimental apparatus dedicated to the research of liquid and solution samples is presented.