OPTICAL AND EPR SPECTROSCOPIC STUDIES OF SILVER CLUSTERS IN AG,NA-Y ZEOLITE BY GAMMA-IRRADIATION

Silver clusters in gamma-irradiated faujasite (zeolite Y) have been st udied and characterized by optical absorption and electron paramagneti c resonance (EPR) spectroscopies. Depending upon the composition and c onditions of preparation (silver and water content, irradiation dose), different silver cluster species and silver particles were observed. A new silver cluster species inside the faujasite lattice, which corre sponds to a low silver content, is presented. Optical absorption bands at 265 and 305 nm have been observed and assigned to trimeric silver ions (Ag-3(2+)). In addition, EPR data of the dehydrated low-silver-co ntent samples indicated the formation of trimeric silver clusters (Ag- 3(0)) with an isotropic EPR signal (g(iso) = 2.034, coupling constant of 90-100 G) and no detectable hyperfine splitting. These silver clust ers are probably linear.