A study of the electric quadrupole Raman processes of the proton‐conducting KHSeO 4 and KDSeO 4 single crystals using 1 H, 2 H and 39 K NMR

The spin–lattice relaxation time, T 1 , and the spin–spin relaxation time, T 2 , of the 1 H, 2 H, and 39 K nuclei in KHSeO 4 and KDSeO 4 crystals were determined in the temperature range 160–420 K. The T 1 of the 39 K nuclei in the two crystals were found to decrease with increasing temperature, and the spin–lattice relaxation rate, T 1 –1 , for 39 K is proportional to T k . In the case of KHSeO 4 , T 1 –1 for the 39 K nuclei was found to have a very strong temperature dependence, i.e. it is proportional to T 7 . The temperature dependence of the 39 K relaxation rate in KDSeO 4 is in accordance with a Raman process, as T 1 –1 ∝ T 2 . Thus, for the 39 K nuclei in the two crystals, Raman processes with k = 2 and 7 is due to the coupling of electric quadrupole moments to the thermal fluctuations of the local electric field gradients. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)