Phonon relaxation processes in crystals (NaNO3) at high pressure and low temperature.

NaNO3 is investigated in a diamond anvil cell in the pressure range of 0–9 GPa at 21 and 142 K by means of high-resolution Raman spectroscopy (HRRS). The pressure dependent linewidth of ν1 (symmetric stretch) is determined and discussed in the framework of anharmonic lattice dynamics. The main relaxation pathways are depopulation processes which are influenced by anharmonic terms in the expansion of the crystal potential and by multiphonon densities of states. The interpretation is supported by numerical calculation of multiphonon densities of states. [ABSTRACT FROM AUTHOR]