Raman spectra of the lattice vibrations of solid nitrogen near room temperture

Low-frequency peaks begin to appear in Raman spectra of solid N2 when δ-N2 transforms to either the ϵ- or η-N2 phase and orientational order develops in δ-N2. These same peaks are known at 15 K but are very much broader at the higher temperatures. Near the phase boundaries, these peaks are extremely weak and remain weak even under the best of conditions. We have used Raman spectra of these modes to map the δ-ϵ and δ-ϵ phase boundaries.