Reorientational Motion of NH 4 Ions in (NH 4 ) 2 SbF 5 Quasielastic Neutron Scattering Study

(NH 4 ) 2 SbF 5 has orthorhombic structure at room temperature. It has two crystallographically inequivalent NH 4 ions in the unit cell. Neutron quasi‐elastic scattering study is made of reorientational motion of NH 4 ions in this salt. Experiments are carried out at 300, 180, and 160 K in the wave vector transfer region of 10 to 23 nm −1 . Measured ratio of elastic to quasi‐elastic intensity as a function of wave vector transfer suggests that the two NH 4 ions have similar reorientation times measurable within the time window of the spectrometer namely, in the range of 3 to 75 ps. The average form factor A (Q) and the average reorientation time, τ = (10 ± 3) ps, associated with the two NH 4 ions are obtained. Broadening of the elastic peak is not seen at 180 or 160 K. This suggests that at these temperatures the value of τ is more than 75 ps.