Raman processes of KNaSO4 and K3Na(SO4)(2) single crystals studied by Na-23 and K-39 nuclear magnetic resonance

Abstract

The spin-lattice relaxation rate, T, 1, of the Na-23 and K-39 nuclei in KNaSO4 and K3Na(SO4)(2) crystals was determined in the temperature range 160-420 K. The results showed similar temperature dependences of T-1(-1) for both types of nuclei, indicating that the local environment has an important influence on T-1(-1) of the metal nuclei. Moreover, the T values of the Na-23 and K-39 nuclei in the two crystals were found to increase with increasing temperature, and T-1(-1) was determined to be proportional to T-k for both metals. In the case of KNaSO4 and K3Na(SO4)(2), T-1(-1) was found to have a temperature dependence proportional to f-, indicating that Raman processes may be responsible for the relaxation of the Na-23 and K-39 nuclei. Therefore, for the Na-23 and K-39 nuclei in the two crystals, Raman processes with k = 2 are more effective in nuclear quadrupole relaxation than direct processes. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim