Acoustic velocities, refractive index, and elastic constants of liquid and solidCO2at high pressures up to 6 GPa

Acoustic velocities, refractive index, and elastic constants of liquid and solid ${\mathrm{CO}}_2$ have been determined at pressures up to 6 GPa by applying Brillouin spectroscopy developed for condensed gases in a diamond-anvil high-pressure cell. The analyses of the angular dependence of Brillouin acoustic velocities show that the solid ${\mathrm{CO}}_2$ remains in the cubic (dry ice) phase I throughout the range of pressure from freezing (0.6 GPa) to 6 GPa at 300 K.