Compression of Ar(H2)2up to 175 GPa: A new path for the dissociation of molecular hydrogen?

Optical observations, Raman scattering, and single-crystal synchrotron x-ray measurements demonstrate the stability of a new stoichiometric compound, Ar(${\mathrm{H}}_2$ ${)}_2$. This is a Laves phase with a hexagonal structure isomorphous to ${\mathrm{MgZn}}_2$. A first order phase transition, wihch is associated with the sudden disappearance of the vibron and a visual increase absorbance of the sample, was observed around 175 GPa in three different experiments, two on Ar(${\mathrm{H}}_2$ ${)}_2$ and one on Ar(${\mathrm{D}}_2$ ${)}_2$. Optical absorption measurements up to 200 GPa in Ar(${\mathrm{D}}_2$ ${)}_2$ have revealed the onset of a possible Drude type metallic behavior above the transition.