Fluid molecular oxygen becomes metallic

Fluid molecular oxygen becomes metallic at a pressure of 1.2 Mbar and a temperature around 4500 K. Physicists at the Lawrence Livermore National Laboratory fired a projectile at a reservoir of liquid oxygen trapped between two single-crystal sapphire anvils. The resulting shock-wave was multiply reflected between the anvils, gradually raising the pressure and compressing the liquid sample. The final steady-state conditions under which the resistivity measurements were made lasted for 100–200 ns. At 77 K and 1 bar, liquid oxygen is a wide-bandgap electrical insulator. As they squeezed it, however, the researchers saw the resistivity fall by six orders of magnitude and level off above 1.2 Mbar as the distance between the diatomic molecules became comparable to the electronic wavefunction. The experimental technique is similar to that used to create metallic hydrogen (see Physics Today, May 1996, page 17 ) The researchers note that the temperatures and pressures achieved in their experiments are comparable to those within the gas-giant planets, where oxygen is abundant. Thus, their work may help explain the origin of planetary magnetic fields. (M. Bastea, A. C. Mitchell, W. J. Nellis, Phys. Rev. Lett. 86, 3108, 2001 http://dx.doi.org/10.1103/PhysRevLett.86.3108 .)