OPTICAL-ABSORPTION SPECTRA OF FLUID SELENIUM NEAR THE NONMETAL-METAL TRANSITION REGION

The optical absorption coefficient of fluid Se was measured in the energy range of 0.5-4.5eV at temperatures up to 1700°C and pressures up to 500 bar. Measurements were made by use of quartz and sapphire cells. The optical path lengths were 5mm to 3000A, which enabled us to obtain the absorption coefficient in the wide range extending to the value of 2×105cm-1. The optical gap was for the first time derived derived from the analysis of the spectra in such a high absorption region. The optical gap substantially decreases with temperature and pressure eventually to vanish near the liquid-gas critical point. © 1990.