Metallization of Fluid Molecular Hydrogen at 140 GPa (1.4 Mbar)

Electrical resistivities were measured for liquid ${\mathrm{H}}_2$ and ${\mathrm{D}}_2$ shock compressed to pressures of 93–180 GPa (0.93–1.8 Mbar). Calculated densities and temperatures were in the range 0.28–0.36 mol/c${\mathrm{m}}^3$ and 2200–4400 K. Resistivity decreases almost 4 orders of magnitude from 93 to 140 GPa and is essentially constant at a value typical of a liquid metal from 140 to 180 GPa. The data are interpreted in terms of a continuous transition from a semiconducting to metallic diatomic fluid at 140 GPa and 3000 K.