Raman study of carbon dioxide up to 80 GPa

Abstract

In order to investigate the phase transition of solid CO₂ under high pressure, Raman measurements were performed up to 80 GPa at room temperature using a diamond anvil cell. To reduce the strain in the sample, an indium metal was used as the pressure medium. The Raman spectrum of the molecular phase III was found to be changed around 65 GPa; the Raman intensities for the lattice modes were suddenly weakened without gradual broadening, strongly suggesting a structural phase transition. In the decompression process, the high-pressure phase did not return to phase III but to phase I, which is the lowest pressure phase of CO₂.

Keywords:

• Carbon dioxide
• Raman scattering
• Structural phase transition
• Pressure medium