Origin of the lambda transition in liquid sulfur

Developing a novel experimental technique, we applied photon correlation spectroscopy using infrared radiation in liquid sulfur around T-lambda, i.e., in the temperature range where an abrupt increase in viscosity by 4 orders of magnitude is observed upon heating within few degrees. This allowed us-overcoming photoinduced and absorption effects at visible wavelengths-to reveal a chain relaxation process with characteristic time in the millisecond range. These results do rehabilitate the validity of the Maxwell relation in sulfur from an apparent failure, allowing rationalizing of the mechanical and thermodynamic behavior of this system within a viscoelastic scenario.