Spin-lattice relaxation below superprotonic phase transition in Rb 3H(SeO 4) 2

Abstract

In order to investigate the proton dynamics and the mechanism of the relatively high-electrical conductivity observed even below T c in Rb 3H(SeO 4) 2, we have measured the 1H spin-lattice relaxation rate. From the measurement of the 1H spin-lattice relaxation rate T 1 − 1 , it is found that the temperature dependence of T 1 − 1 takes a peak at around 345 K. The analysis of the temperature dependence of T 1 − 1 shows that T 1 − 1 in Rb 3H(SeO 4) 2 is described well by the dipole–dipole relaxation between proton and Rb nuclei. Moreover, it was also found that not only the proton dynamics described by a hopping motion of proton between two equivalent sites in the hydrogen bond but also a new process of proton transfer appears above around 338 K. This new process is a hopping motion of proton accompanied by the breaking and rearrangement of hydrogen bond. From these results it is deduced that the increase of the electrical conductivity observed even below T c is caused by the proton transfer between possible stable sites accompanied by the breaking and rearrangement of hydrogen bond, and that electrical conductivity in Rb 3H(SeO 4) 2 is dominated by protons motion even below T c.