S-K-BETA X-RAY-FLUORESCENCE SPECTRA OF THE TL-2-S-SB2S3 CHALCOGENIDE SYSTEM

The sulphur 3p valence states of Sb2S3, Tl3SbS3, TlSbS2, TlSb3S5, TlSb 5S8, and Tl2S of the Tl2S-Sb2S3 system have been investigated by means of the S K beta (3p --> ls) x-ray emission band. TlSb3S5 and TlSb5S8 were also studied in the glassy phase. Synchrotron-radiation-induced f luorescence was used. The spectra are discussed in terms of bonding be tween the sulphur atoms and their nearest neighbours with the help of tight-binding calculations. We observe significant differences among t he S 3p states of all these materials, including between the crystalli ne and glassy phase of TlSb3S5. The variations in the S K beta bandwid th and shape clearly reflect the sensitivity of the S 3p states to the local environment and indicate that the valence densities of states a re mainly influenced by local order.