Scattering of Cold Neutrons in Ammonium Carbonate, Ammonium Citrate, and Ammonium Acetate

Neutron-energy-gain spectra have been measured in (NH4)2CO3, (NH4)2HC6H5O7, and NH4C2H3O2 at 20°C using the Brookhaven slow-chopper facility. Each spectrum exhibits two peaks that are characteristic of optical modes. The spectra of ammonium carbonate and ammonium citrate are similar to those of the body-centered-cubic lattice phase of the ammonium halides in which the ammonium ion has torsional and translational optical vibrations.