Abstract
We describe the features of a polarization-dependent total-reflection fluorescence EXAFS technique (TPRF EXAFS) and its application to Mo/TiO2(110) systems. This technique uses the polarization dependence of EXAFS expressed by the following equation, χ(k)=3Σicos2θi · χi(k), where θi and χi are an angle between electric polarization vector and the i-th bond direction and an EXAFS oscillation accompanying i-th bond, respectively. By changing the orientation of the sample against polarization vector, we can obtain 3-dimensional information of the chemical species dispersed on surface. TPRF EXAFS has revealed how Mo species on TiO2(110) changes its structure depending on the preparation conditions. Mo dimer species is stabilized under oxidative conditions while Mo chain is present under reductive conditions. We would like to stress that the TPRF EXAFS has become a practical tool for a characterization of 3 dimensional local structures of active sites on model supports.
