Absorption measurements are carried out on solid molecular hydrogen to 172 GPa at 295 K in a diamond-anvil cell from 0.5 to 3.0 eV. Analyses of both absorption and reflectance spectra provide complementary constraints on Drude-model parameters under the assumption that the band gap has closed at the highest pressures. Contributions from interband and vibrational transitions, optical effects associated with preferred orientation of the hydrogen, and stress-induced changes in the diamond refractive index are also examined.

• Received 30 October 1990

DOI:https://doi.org/10.1103/PhysRevB.43.8767