Raman spectra of sulfur, selenium or tellurium clusters confined in nano-cavities of zeolite A

Raman spectra of sulfur, selenium and tellurium clusters confined in the large cavities of zeolite A with diameters of similar to 1.4 nm have been studied. It is shown that sulfur is stabilized in the form of S-8 rings. Selenium is stabilized in the form of Se-12 and Se-8 rings. Se-12 rings show dominant bands in the Raman spectra but they are less stable than Se-8 rings under laser illumination with a wavelength of 514.5 nm. Tellurium is stabilized in the form of Te-8 rings. Low-frequency strong and broad bands at similar to 40 cm(-1) and similar to 29 cm(-1) observed in the spectra of zeolite A with sulfur and with selenium, respectively, are attributed to librations of the ring molecules in the zeolite cavities. (C) 1998 Published by Elsevier Science Ltd.