TEMPERATURE DEPENDENCE OF THE RAMAN FREQUENCIES IN THE γ AND β PHASES OF SOLID NITROGEN

We study here the Raman frequencies of the lattice modes (gamma and beta phases) and of an internal mode (gamma phase) as a function of temperature in solid nitrogen. The frequency shift, derived from the anharmonic self energy, is fitted to the experimental data for the Raman frequencies of the modes considered here in the gamma and beta phases of solid nitrogen. From our fittings, we find that the Raman frequencies of the lattice modes decrease, whereas those of the internal mode increase with increasing temperature in solid nitrogen. The unusual behavior of the internal mode indicates that the interaction mechanism should be different in relation to the anharmonicity in the gamma phase of solid nitrogen.