Ammonium ion diffusion in (NH4)3H(SO4)2 was studied by means of 1H spin-lattice relaxation times in the rotating frame, T1ρ. The 1H T1ρ values were measured at 200.13MHz and 380 to 490K. The ammonium protons and the acidic protons had independent T1ρ values; suggesting that the spin diffusion between the 2 species was ineffective. The translational diffusion of the ammonium ions was the most dominant mechanism to relax both the ammonium protons and the acidic protons in phase I. The 1H T1ρ values in phase I were analyzed theoretically and the motional parameters were obtained. The activation energy (Ea) was 75kJ/mol and the mean residence time at the infinite temperature (τ0) was 4.0 x 10−15s. This motion was 3 or 4 orders of magnitude slower than that of the acidic protons.

Ammonium Ion Diffusion in the Superprotonic Phase of (NH4)3H(SO4)2 as Studied by 1H Spin-Lattice Relaxation Times in the Rotating Frame. H.Omi, K.Suzuki, S.Hayashi: Solid State Ionics, 2008, 178[35-36], 1792-7