A NEW DETERMINATION OF THE BINARY PHASE-DIAGRAM OF H2-HE MIXTURES AT 296-K

The properties of dense H-2-He mixtures have been measured in a diamond anvil cell (DAC) at T = 296 K by direct visualization and Raman spectroscopy. The discrepancies that existed between the two previous high-pressure works have been resolved; they stemmed from an underestimation of the homogenization time of the mixture which is prepared for loading the DAC. The Raman spectroscopy measurements confirm the existence of a cusp on the fluid-fluid coexistence curve. The miscibility of one component in the solid of the other has also been investigated.