Tunnelling of the one-dimensional rotor NH3D+ in the NH4ClO4 and NH4PF6 lattices Original Research Article

Inelastic neutron scattering (INS) spectra of partially deuterated NH4PF6 and NH4ClO4 were measured to investigate the tunnelling of the rotor NH3D+ in environments of low symmetry. Rotational tunnelling of NH3D+ appears clearly as a single peak at about the same energy as the TE transitions in the fully protonated crystals. The presence of a single peak indicates that the D atom is localized, and tunnelling is strictly 1-dimensional about the ND bond direction. There is no evidence for tunnelling of NH2D2+.