ABSORPTION AND RAMAN-SPECTRA OF SE-8-RING CLUSTERS IN ZEOLITE 5A

Samples with different weight ratio of Se to zeolite 5A (Se compositio n) have been prepared by loading Se into the cages of zeolite 5A and t he measurements of the absorption and Raman spectra have been carried out for the prepared samples. The measured absorption edges of the sam ples close and blue shifted to the value for monoclinic Se containing Se-8-ring, suggesting the formation of Se-8-ring clusters dagger in th e cages. The continuous and broadening features of the absorption spec tra are interpreted by the strong electron-phonon coupling in Se-8-rin g clusters. The sample with high Se composition has a red shift of the absorption band edge relative to the samples with less Se composition . It is tentatively attributed to the reason that with different Se co mposition, single Se-8-ring clusters and double Se-8-ring clusters are formed in the cages of zeolite 5A. A single broad band at about 262 c m(-1) is observed in the Raman spectra, that gives the further support of the formation of Se-8-ring clusters. Copyright (C) 1996 Elsevier S cience Ltd