Study of molecular motion by 1 H NMR relaxation in ferroelectric LiH 3 (SeO 3 ) 2 , Li 2 SO 4 ·H 2 O, and LiN 2 H 5 SO 4 single crystals

The proton NMR line widths and spin-lattice relaxation rates, T1, of ferroelectric LiH3(SeO3)2, Li2SO4·H2O, and LiN2H5SO4 single crystals were measured as a function of temperature. The line width measurements reveal rigid lattice behavior of all the crystals at low temperatures and line narrowing due to molecular motion at higher temperatures. The temperature dependences of the proton T1 for these crystals exhibit maxima, which are attributed to the effects of molecular motion by the Bloembergen Purcell Pound theory. The activation energies for the molecular motions of H in these crystals were obtained. From these analysis, H in LiH3(SeO3)2 undergoes molecular motion more easily than H in LiN2H5SO4 and Li2SO4·H2O crystals.