A detailed analysis of the excitation and recombination processes of the charge carriers in CdIn2S4 crystals is discussed. The luminescence spectra and the luminescence excitation spectra at temperatures ranging from liquid helium temperature to room temperature are presented; the effect of a secondary low energy radiation on luminescence is also discussed. Models are proposed for the excitation and recombination processes and a scheme of the levels localized in the gap of CdIn2S4. The two emission bands observed are attributed to an interimpurity recombination and to an electron transition between a donor level and the valence band, respectively; the presence of a non radiative recombination process is also proposed.

The photoluminescence of CdIn2S4 single crystals grown using the Bridgman technique is analysed in detail; the effect of different treatments (thermal treatments in various atmospheres, electrodiffusions, and γ‐irradiation) on the shape of the emission bands is studied. From this analysis one of the two emission bands which characterize the CdIn2S4 luminescence can be attributed to a centre formed by a sulphur vacancy; the other band is due to a centre probably connected to some kind of intrinsic disorder characteristic of CdIn2S4 (exchange Cd ⇆ In for instance) and not to a stoichiometric defect.

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Optical absorption and electron spin resonance (ESR) attributed to X‐ray induced localized paramagnetic states are studied in glassy As2Se3 and As2Se3 for T ≧ 77 K. The production of induced paramagnetic states is not detected in crystalline As2S3. X‐ray irradiation of a crystal at 77 K excites luminescence with the same spectrum as that for photoluminescence. No X‐ray excited luminescence is observed in glasses at 77 K. It is shown that a unified explanation for the data can be given on the basis of the Mott‐Davis‐Street model.