X-ray absorption of bromonaphthalene dissolved in supercritical fluid xenon

Abstract

The results of Br K-edge X-ray absorption measurements of 1-bromonaphthalene dissolved in supercritical¯uid Xe are reported. As the pressure of Xe con®ned in a high-pressure cell is increased, the absorption spectrum of bromonaphthalene gradually appears, showing that Xe in the supercritical¯uid state solvates the bromonaphthalene molecule. The spectrum of the dissolved sample shows a remarkable difference from that of the pure liquid sample in the near-edge region of the X-ray absorption spectrum, re¯ecting the interaction of the solute material with solvent Xe. Ab initio full multiple-scattering calculations can reproduce the spectral features qualitatively. A large value of the Debye±Waller factor must be introduced to give the best ®t, corresponding to a large degree of spatial disorder and violent thermal vibration of the Xe atoms around the Br atom.

Full Multiple Scattering Approach to X-Ray Absorption near Edge Structure Spectra of Bromonaphthalene in Supercritical Xenon

“…1 Figure 1 shows the measured normalized Br K-edge X-ray absorption near-edge structure (XANES) spectra of Br Nph in the 2 mol% hexane solution and of the sample dissolved in SCF Xe. 8) This data has already been presented in ref. 8; however, we show them again for the purpose of later discussion.…”

“…8) Therefore, the detailed comparison with the calculated result in ref. 8 will not be shown in this paper.…”

“…8 we show the calculated result for the six Xe coordination model; three Xe are coordinating the Br atom from the upper side and other three from the lower side of the Nph plane. In this model, Xe-Br and Xe-C should be larger than the sum of the van der Waals radii.…”

Solvation structure of impurity molecules in supercritical fluids studied by photoconductivity measurement and X-ray absorption fine structure (XAFS) spectroscopy

“…The XANES spectra shown in Fig. 2 wereanalyzed by Professor T. Fujikawa ofChiba University in terms of an ab initio calculation [4,5]. According to their calculation, xenon atoms surrounding Br atom were very &ive for spectral shape and six or more than xenon atoms associate.…”

“…Recently a X-ray absorption spectroscopy (XAFS) experiment was perfbrmed [4] 6 r bromonaphthalene molecule doped in supercritical xenon ffuids in an attempt to get the direct infbrmation on local solvation structure.…”