Infrared Properties of Ortho and Mixed Crystals of Solid Deuterium at Megabar Pressures and the Question of Metallization in the Hydrogens

Abstract

We have studied the infrared absorption spectra of mixed ortho-para and pure ortho deuterium crystals down to liquid helium temperatures and pressures to 194 GPa in search of an insulator-metal transition. Band theory suggests metallization in this range, where densities are increased more than 10 fold. Our energies extend down to 0.37 eV, the lowest yet reported. No clear evidence of metallization is found, according to a Drude analysis. Significant changes in the spectra are observed when mixed ortho-para samples are converted to pure ortho ${\mathrm{D}}_2$.