Vibrational-Spectra of Crystalline Ammonium-Nitrate

Abstract

The low-temperature Raman spectra of NH₄NO₃ and ND₄NO₃ give evidence of one phase (phase V) with the phase transition from phase IV being sluggish and occuring over a temperature range of some 100 K with pronounced hysteresis . The spectra were consistent with the reported powder structure of P4₂. The internal vibrations of the nitrate ion showed both site and factor group components while the internal motions of the ammonium ion showed evidence of two different coulombic sites with a small site splitting evident for both sites.

In the higher temperature phase some evidence relating to heteroionic coupling of A_g site components in phase IV is presented and the site splitting of internal nitrate bands in CsCl type structures of phases V, IV, II and I is discussed.