Photo-acoustic spectroscopy and EXAFS methods were used to study CdS micro-clusters in Y zeolite or mordenite. Photo-darkening and photo-bleaching were observed at low temperatures. In the zeolite, 4 new absorption bands (2, 2.3, 2.9, 3.4eV) were produced by light with an energy that corresponded to the band gap at low temperatures. The optical properties appeared to be sensitive to the annealing temperature during sample preparation. The photo-darkening and photo-bleaching were explained in terms of defect creation and annihilation.

T.Moyo, K.Maruyama, H.Endo: Journal of Physics - Condensed Matter, 1992, 4[26], 5653-64