STOPPED-FLOW X-RAY ABSORPTION SPECTROSCOPY IN DISPERSIVE MODE

Abstract

new stopped-flow device particularly suitable for X-ray absorption spectroscopy in dispersive mode has been built. Time-resolved measurements of X-ray absorption spectra have been made for reactions in mixed solutions of (i) iron(II1) nitrate and catechol and (ii) iron(II1) nitrate and sodium thiosulfate with time resolutions of -5 ms to a few seconds. Two-step variation of the spectra was observed for the former reaction, while one-step variation for the latter. Introduction Using the energy dispersive X-ray absorption spectrometer/l-3/, a whole profile of an absorption spectrum of interest can be recorded simultaneously without any mechanical motion during the measurement. Thus, the method is suitable for time resolved X-ray absorption spectroscopy. Preliminary results of time resolved experiments using dispersive X-ray absorption spectrometers were reported by Matsushita et a1.141, Fontaine et a1.151 and Sayers et a1.161. In these proceedings Tourillon et a1.171 also give more detailed report on the time-resolved in-situ investigation of the inclusion of metallic aggregates within a conducting polymer using the dispersive EXAFS technique. In the present paper we report the present status of the stopped-flow experiment for kinetic studies of reactions in solutions using the dispersive X-ray absorption spectrometer at the Photon Factory. The stopped-flow method using optical absorption in visible region is an established technique in studying kinetics of reactions in solutions. In the X-ray region, stopped-flow scattering experiments were performed using synchrotron radiationJ8-101. In one/lO/ of these works, a new stopped-flow device having a slit type mixer was developed and used, which give uniform mixing over a large window area of the observation cell. In the previous report/4/, we used this type of device for the preliminary stopped-flow Article published online by EDP Sciences and available at http://dx.doi.org/10.1051/jphyscol:19868104