X-ray Raman spectra of liquid, sub- and super- critical water at the oxygenK-edge were measured, at densities 1.02 - 0.16 gcm^-3. Measurements were madealong both an isotherm and an isochore passing near the critical point. Asdensity is reduced there is a general tendency of the spectra to increasinglyresemble that of the vapor phase, with, first, a well separated low-energypeak, and, eventually, at densities below the critical density, peaks appearingat higher energies corresponding to molecular transitions. The critical pointitself is distinguished by a local maximum in the contrast between some of thespectroscopic features. The results are compared to computed X-ray absorptionspectra of supercritical water.
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