Vacuum Ultraviolet Spectroscopy of the Lowest-Lying Electronic State in Sub-Critical and Supercritical Water
Marin, Timothy W.
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https://hdl.handle.net/2142/91564
Description
Title
Vacuum Ultraviolet Spectroscopy of the Lowest-Lying Electronic State in Sub-Critical and Supercritical Water
Author(s)
Marin, Timothy W.
Contributor(s)
Chipman, Dan
Bartels, David M.
Janik, Ireneusz
Issue Date
2016-06-24
Keyword(s)
Synchrotron text
Abstract
We report vacuum ultraviolet absorption spectra for the lowest-lying electronic state of high-temperature and supercritical water, where spectra were measured from room temperature up to the critical temperature, and as a function of density above the critical temperature. Spectra are seen to redshift with increasing temperature, demonstrating gradual breakdown of the hydrogen bond network. Above the critical temperature, tuning the density gives direct insight into the extent of hydrogen bonding in the supercritical regime. The known gas-phase monomer spectrum can be duplicated in the low-density limit, with negligible contribution from hydrogen bonding. With increasing density, the spectrum blue shifts as small water clusters form, increasing the number of hydrogen bonds lowering the ground-state energy. The presence of vibrational structure inherent to the lowest-density gas-phase limit spectrum gradually diminishes with increasing density, giving a reasonable measure of the extent of water monomers having unperturbed electronic structure as a function of density.
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