Structure Analysis of Solution Surface by Photoelectron Yield XAFS Method.

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The X-ray absorption fine structure (XAFS) spectroscopy is a powerful tool for the short range structure analyzes of amorphous samples and liquids. In this study its application is extended to the chemical species at air/water interface. The surface active ions and molecules segregated at the solution surface are playing important role in the processes of solvent extraction, phase -transfer, and the formation of the Langmuir-Blodgett film, although almost nothing is known about the solvation structures of the surface species.The monochromatized X-ray beam was introduced into the solution cell at a grazing incidence angle of 1mrad under the total-reflection condition. The cell contains a 66mm x 216mm trough which is cooled to 1? A1C and the cell is filled with helium gas at an atmospheric pressure. The XAFS of the surface species was determined by detecting the conversion electron current or the helium ion current. Stearyltrimethylammonium bromide aqueous solution at 0.1mM concentration gave quite an intense signal for Br K-edge absorption. The spectrum was different from that of bulk solution by the transmission method.