Coherent anti-Stokes Raman spectroscopy of highly compressed solid deuterium at 300 K: Evidence for a new phase and implications for the band gap

Coherent anti-Stokes Raman spectroscopy has been used to study deuterium at ambient temperature to 187 GPa, the highest pressure this technique has ever been applied. The pressure dependence of the nu(1) vibron line shape indicates that deuterium has a rho(direct)=0.501 and rho(exciton)=0.434 mol/cm(3) for a band gap of 2 omega(P)=4.66 eV. The extrapolation from the ambient pressure band gap yields a metallization pressure of 460 GPa, confirming earlier measurements. Above 143 GPa, the Raman shift data provide clear evidence for the presence of the ab initio predicted I-' phase of deuterium.