HIGH-PRESSURE OPTICAL STUDIES ON SULFUR TO 121 GPA - OPTICAL EVIDENCE FOR METALLIZATION

The pressure dependence of the optical absorption edge to 78 GPa and the reflectivity to 121 GPa were measured in sulfur from 0.5 to 3.5 eV in a diamond anvil cell. Our optical results show no evidence of metallic behavior below 95 GPa. A discontinuous change in absorption was observed at 23 GPa. The absorption edge is about 1 eV at 50 GPa, the pressure at which poor metalliclike behavior of sulfur was suggested earlier based on the measurement of the temperature dependence of the electrical resistance. At 95 GPa the reflectivity has a sudden increase and reaches 62% in the infrared range at the sample-diamond interface at 121 GPa. We attribute this to pressure-induced metallization.