Shock compression of deuterium near 100 GPa pressures

The shock-compression curve (Hugoniot) of D-2 near 100 GPa pressures (1 Mbar) has been contro-versial because the two published measurements have limiting compressions of fourfold and sixfold. Our purpose is to examine published experimental results to decide which, if either, is probably correct. The published Hugoniot data of low-Z diatomic molecules have a universal behavior. The deuterium data of Knudson et al. (fourfold limiting compression) have this universal behavior, which suggests that Knudson et al. are correct and shows that deuterium behaves as other low-Z elements at high tem-peratures. In D-2, H-2, N-2, CO, and O-2, dissociation completes and average kinetic energy dominates average potential energy above similar to60 GPa. Below similar to30 GPa, D-2, H-2, N-2, CO, and O-2 are diatomic. D-2 dissociation is accompanied by a temperature-driven nonmetal-metal transition at similar to50 GPa.