Optical spectra of liquid water in vacuum uv region by means of inelastic x-ray scattering spectroscopy

What is it about?

Inelastic x-ray scattering (IXS) spectroscopy using hard x-rays is in principle equivalent to optical spectroscopy as long as momentum transfer can be approximated to be zero. Hence IXS spectra of liquid water which corresponds to vacuum uv absorption were measured at small energy transfers with energy resolution of 0.5 eV. The loss function was derived from the spectra and its convergence for the momentum transfer smaller than 0.28 a.u. was confirmed. It is shown that the optical oscillator strength of liquid water differs considerably from that of gaseous water.

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Why is it important?

This study demonstrates that IXS spectroscopy is an invaluable tool for the determination of optical oscillator strength of volatile liquids in the VUV-SX region. Such a measurement is almost impossible by conventional spectroscopies.