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Probing the Hydrogen-Bond Network of Water via Time-Resolved Soft X-Ray Spectroscopy Print
Thursday, 28 May 2009 00:00

We report time-resolved studies of hydrogen bonding in liquid H2O, in response to direct excitation of the O–H stretch mode at 3 m, probed via soft X-ray absorption spectroscopy at the oxygen K-edge. This approach employs a newly developed nanofluidic cell for transient soft X-ray spectroscopy in the liquid phase. Distinct changes in the near-edge spectral region (XANES) are observed, and are indicative of a transient temperature rise of 10 K following transient laser excitation and rapid thermalization of vibrational energy. The rapid heating occurs at constant volume and the associated increase in internal pressure, estimated to be 8 MPa, is manifested by distinct spectral changes that differ from those induced by temperature alone. We conclude that the near-edge spectral shape of the oxygen K-edge is a sensitive probe of internal pressure, opening new possibilities for testing the validity of water models and providing new insight into the nature of hydrogen bonding in water. Article Link (PDF)