High-pressure Raman scattering of the stretching mode in nitrogen along the 300-K isotherm

We present Raman scattering studies of the vibrational band of nitrogen at room temperature between 1 and 31 GPa allowing a detailed line-shape analysis. For the fluid and β phases the vibrational linewidths compare to dephasing rates ${\mathit{T}}_2^{\mathrm{-}1}$ determined by experiments in the time domain. The δ-ε transition is unmistakably marked by a drop of the vibrational linewidths around 17 GPa. A further transition into the η phase around 20 GPa proposed from previous Raman results can be ruled out. Additionally, clear evidence is found for a dynamical freezing of the ${\mathrm{N}}_2$ molecules within the δ phase. © 1996 The American Physical Society.