Raman spectroscopy on high-pressure fluids of molecular oxygen and nitrogen

High-pressure Raman scattering experiments of O2 and N2 were carried out at 296 K and at pressures up to 10 and 6 GPa, respectively, and the pressure dependence of vibrational spectra of O2 was studied on the basis of molecular interactions in comparison with N2. An appreciable contribution of the attractive interaction to the vibrational frequency was observed for fluid O2. The linewidth of the spectra for fluid O2 showed a sharp increase with increasing pressure, and the fluid–solid transition was observed at 5.9 GPa with a sudden drop of the linewidth.