Absorption and Raman spectra of Se₈-ring clusters in zeolite 5A

Samples with different weight ratio of Se to zeolite 5A (Se composition) have been prepared by loading Se into the cages of zeolite 5A and the measurements of the absorption and Raman spectra have been carried out for the prepared samples. The measured absorption edges of the samples are close and blue shifted to the value for monoclinic Se containing Se₈-ring, suggesting the formation of Se₈-ring clusters † in the cages. The continuous and broadening features of the absorption spectra are interpreted by the strong electron-phonon coupling in Se₈-ring 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 composition, single Se₈-ring clusters and double Se₈-ring clusters are formed in the cages of zeolite 5A. A single broad band at about 262 cm^-1 is observed in the Raman spectra, that gives the further support of the formation of Se₈-ring clusters.