Raman Study of Nitrogen at High Pressure

Raman spectra of the nitrogen loaded in a diamond anvil cell with the compressed gas have been investigated at the pressure up to 40GPa. Pressure was measured in terms of the ruby fluorescence. The curve of frequency vs pressure was obtained by micro-Raman spectrometer. According to the experimental results, the frequency of two stretching mode peaks increases steadily from 2340 and 2347cm^-1 at 5.2 GPa to 2396 and 2434 cm^-1 at 40 GPa, respectively. The interval between two peaks also increases gradually with pressure increasing. A new peak (2402cm^-1) of the stretching mode was observed near 40 GPa, which may be associated with the distortion of the Pm3n structure or the formation of low-symmetry structure.