Inelastic neutron scattering and potential shape in ammonium hexachlorides

Abstract

Investigations of inelastic neutron scattering in cubic ammonium hexachlorides that have almost identical structures give the following energies E1 for the first excited NH4+ torsional state at 82K: 7.5 meV for (NH4)2PdCl6, 8 meV for (NH4)2PtCl6, 14.5 meV for (NH4)2SnCl6, 15.5 meV for (NH4)2PbCl6 and 18 meV for (NH4)2TeCl6. The relation between E1 and activation energies Ea for NH4+ reorientation from proton relaxation differs from that of most other ammonium salts. The shape of the potential seen by NH4+ is discussed Ea and E1 are found to be very sensitive functions of the structure parameters.