FLUID-STRUCTURE IN SUPERCRITICAL XENON BY NUCLEAR-MAGNETIC-RESONANCE SPECTROSCOPY AND SMALL-ANGLE X-RAY-SCATTERING

Chemical shifts for Xe-129 at 25 degrees C are presented for densities between 5 x 10(-3) and 2.2 x 10(-2) mol/cm(3), corresponding to pressures between 50 and 1000 bar. Also presented art small angle X-ray scattering results for xenon at 28 and 45 degrees C and pressures between 30 and 400 bar. The scattering results reveal the expected increase in aggregation and correlation length near the critical density. The chemical shifts exhibit deviations from the second-order virial equation over a broad range of densities. These deviations are also evident in calculations from integral equation theory. A departure from the cage model of solvent nearest neighbors due to repulsive solvation effects is discussed as a possible source of these deviations.