High-pressure X-ray Raman Study of CO₂-V and N₂

Abstract

　CO₂ transforms to non-molecular phase at > 37 GPa and room temperature and to covalent solid phase (CO₂ V) at higher temperatures. The electronic structure of CO₂ V reveals one σ*-like band observed at ~540 eV, suggesting clear bonding changes to the covalent solid phase. N₂ exhibits strong π* band at 400.6 eV with slightly energy drop at 14-18 GPa, which could be attributed to ε → ζ phase transition.