1H-NMR and 77Se-NMR in CsHSeO4

Measurements of 1H-NMR and 77Se-NMR have been conducted with CsHSeO4, in order to clarify dynamics of proton and SeO4 tetrahedron which is related to transport of proton below and above Tc = 401 K. An NMR absorption line is observed in 1H-NMR measurement and its line width decreases with increasing temperature below Tc, due to the motional narrowing. These results indicate that the mobile proton exists even below Tc. A correlation time τ is estimated from the line width for the mobile proton to be about 10− 4–10− 6 s below Tc. Furthermore it is deduced from 77Se-NMR measurements that the reorientational motion of SeO4 tetrahedron is related to the transport of proton below Tc.