The Optical Properties of Liquid Chalcogens at High Temperature and Pressure

The temperature and pressure variations of optical reflectivity of liquid S, Se, Te, Se 80 Te 20 , Se 50 Te 50 , and Se 20 Te 80 have been measured in the energy range between 0.5 and 5.4 eV. Optical conductivity σ(ω) has been derived by using an oscillator fitting analysis. The σ(ω) curve for liquid S and Se has a broad peak, which is assigned to the optical transition from the lone pair to the antibonding σ * states on the adjacent site in the same chain. At high temperature and high pressure, there appears the Drude term in the σ(ω) curve of liquid Se. In this region, liquid Se is transformed from semiconducting to metallic state, which is accompanied by changes in the thermodynamic properties. The observed broad peak around 2 eV for liquid Te may suggest that the covalently bonded twofold structure remains on melting.