Raman Scattering and Phase Transition in AgNa(NO2)2

Temperature dependence of the Raman spectrum of AgNa(NO 2 ) 2 has been studied. At low temperatures, the ν 2 -spectrum due to the bending vibration of the NO - 2 ions in the crystal consists of two components at 832 and 858 cm -1 . With increasing temperature, the third component becomes appreciable at 845 cm -1 near -40^° C . The third and 858 cm -1 components approach each other as temperature rises and merge together resulting in a broad band above T c . Near 0°C, a weak shoulder becomes appreciable on the high energy tail of 832 cm -1 component. The shoulder and 832 cm -1 component also merge together and become a broad band above T c . The sum of their intensities decreases monotonically as temperature rises and drops remarkably near T c . Assignments are given to the four components of the ν 2 -spectrum by referring to the IR and luminescence spectra of the crystal. The results are also discussed in relation to the phase transition in the crystal.