VIBRATIONAL DENSITY-OF-STATES AND HOMOGENEOUS LINEWIDTH IN MOLECULAR-CRYSTALS - MANY-PHONON PROCESSES IN NITROGEN

This paper summarizes, simplifies, and extends some recent development s in the theory of phonon damping in anharmonic crystals. We propose a n approach in which the damping is described in terms of two ingredien ts: (1) a computed or estimated one-phonon density of states, and (2) average anharmonic couplings between the phonons, fitted to the experi mental temperature dependence of the phonon damping. Solid nitrogen is chosen as a test case and the coupling coefficients obtained from the fit are correlated to the three-, four-, and five-phonon couplings co mputed from a potential model.