Absorption spectra of selenium clusters and chains incorporated into zeolites

Abstract

Absorption spectra are reported for Se adsorbed in faujasite (X or Y) as a function of x, where x is the Al-to-(Al+Si) ratio. The amount of adsorbed Se increases with increasing x for small x and is saturated for x>or approximately=0.1. The results are interpreted using the model in which the finite number of Se atoms are physically adsorbed by each permanent dipole which consists of (AlO₄)^- in a zeolite framework and cation. The energy of the lower absorption edge changes with x and the spectral shapes are classified into three types. Spectral differences are also observed for Se incorporated into Linde type A and Linde type L lattices. From a comparison with the spectrum of the isolated Se chain in mordenite, the structures of Se in A and L are expected to be isolated clusters and double parallel chains, respectively.