EXAFS INVESTIGATIONS OF HIGH-NUCLEARITY PD CLUSTERS

Pd K-edge X-ray absorption spectra at several temperatures of Pd-561(p hen)(36)O-200 and other high nuclearity ligand-stabilized Pd clusters are reported. Data-analysis performed in a wide k-range (up to 17.5 An gstrom(-1)), accounting for possible effects of asymmetry, allowed us to obtain very reliable results for the nearest neighbour Pd-Pd distri bution. Mean bond length and variance are determined as a function of temperature. The data indicate the existence of regular FCC particles with a very weak relaxation with respect to the bulk ideal geometry an d no asymmetry effects in the bond length distribution.