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.

• Received 18 January 1991

DOI:https://doi.org/10.1103/PhysRevLett.67.2998