Optical and electrical effects during polymerization and depolymerization in liquid sulfur: indications for the nonuniformity model for covalent liquids

The polymerization and depolymerization of liquid sulfur refers, respectively, to the processes of chain growth and chain scission promoted by changing thermodynamic conditions. These structural transitions cause major optical and electrical consequences, including: (1) color change from yellow to orange to red, (2) peaked high angle and low angle scattering and minimum in transmission of He-Ne laser light at the structural changes, (3) a decrease in the current induced by a pulsed ruby laser above the polymerization temperature T(p) compared with below T(p), (4) two changes in the sign of the temperature coefficient of resistance in the vicinity of T(p) and the depolymerization temperature T(d), and (5) superlinear current-voltage characteristics above T(d). The data are interpreted as being suggestive of the structure of a liquid being better described by a nonuniformity rather than random network model.