Variations in the absorption spectrum of sulfur vapour and melt at electric discharge, vapour-melt phase transition, and melt polymerization

An effort is undertaken to reproduce the primary steps of formation of poly meric sulfur during plasmochemical decomposition of hydrogen sulfide in an optical cell heated to 450 degreesC; extensive investigation is made into v ariation of the cluster composition of sulfur vapour and its relaxation upo n turning the discharge on and off and into the effect of such factors as i mpurities present in sulfur, temperature and thickness of the melted layer, and optical radiation on polymerization equilibrium in liquid sulfur. It h as been found that with discharge on, sulfur clusters primarily undergo fra gmentation. Subsequent to turning the discharge off, the cluster compositio n relaxes in several minutes, which suggests that this process is controlle d by slow reactions. This fact accounts for the available data on the effec t of cluster composition of vapour on the yield of polymeric sulfur from va pour condensation. An analysis of variations in the absorption spectrum in the course of vapour-liquid state transition has led to the conclusion that absorption of melts results in a new band at the short-wavelength edge of the visible spectrum. This band is assigned to charge transfer complexes - necessary accompaniments of melted-sulfur polymerization. It is shown that changes in the absorption spectrum under the action of different factors, b e it heating, variation of thickness, addition of minor impurities or irrad iation with light, have a common origin, namely, a shift of polymerization equilibrium in a melt, such that the melt composition relaxes slowly, becau se its rate is limited by a polymer chains-charge transfer complexes-S-8 ri ngs series of chemical conversions.