Coherent Anti-Stokes Raman Spectroscopy of Highly Compressed Solid Deuterium at 300 K: Evidence for a New Phase and Implications for the Band Gap

Abstract

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 ${\rho }_{\mathrm{direct}}=0.501$ and ${\rho }_{\mathrm{exciton}}=0.434\mathrm{mol}/{\mathrm{cm}}^3$ for a band gap of $2{\omega }_P=4.66\mathrm{eV}$. 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 ${\mathrm{I}}^{\prime }$ phase of deuterium.