Raman Scattering and Short-Range Order in Ammonium Bromide at theλTransition

Abstract

The decay of short-range ordering of N$\mathrm{H}_4^{}{}_{}{}^{+}$ ions below $T_{\lambda }$ (235°K) in N${\mathrm{H}}_4$Br is shown to be responsible for both the specific-heat anomaly and the Raman scattering of a polarized low-frequency mode at 56 ${\mathrm{cm}}^{-1\mathrm{}}$. The temperature-weighted integrated Raman intensity is quantitatively compared with the residual specific heat below $T_{\lambda }$.