NMR investigation of ionic motion in LiI-KI in the liquid state

¹ Graduate School of Science and Engineering, Niigata University, Ikarashi 2-8050, Nishi-ku, Niigata 950-2181, Japan
² Department of Physics, Faculty of Science, Niigata University, Ikarashi 2-8050, Nishi-ku, Niigata 950-2181, Japan
³ JAXA, Sengen 2-2-1, Tsukuba 305-0047, Japan

Abstract

The longitudinal relaxation time (T₁), transverse relaxation time (T₂), and chemical shift of ⁷Li, and the line width and chemical shift of ¹²⁷I were measured to study ionic motion in the eutectic LiI-KI mixture in the liquid state. T₁ and T₂ of ⁷Li are both very long (more than a few seconds). Motioning narrowing is not observed for ⁷Li, which gives the lower limit of the correlation time, ~10^-9 s. The relaxation times of ¹²⁷I nucleus are too short (less than 100 μs) to measure using the standard pulse methods. Although the resonance peak of ⁷Li is very narrow and the chemical shift is almost independent of temperature and composition, the resonance peak of ¹²⁷I is very broad and dependent on temperature and composition, which has been analyzed by assuming two sites of I^- and their rapid exchange. The residence time of I^- is estimated to be about 10^-5 s.