A study of molecular motion and Raman processes in K3H(SO4)2 and KHSO4 single crystals by observation of 1H and 39 K spin-lattice relaxation

The spin-lattice relaxation rates for H-1 and K-39 nuclei in K3H(SO4)(2) and KHSO4 single crystals, which are potential candidate materials for use in fuel cells, were determined as a function of temperature. The spin-lattice relaxation recovery of H-1 can be represented for both crystals with a single exponential function, but cannot be represented by the Bloernbergen-Purcell-Pound (BPP) function. so is not related to HSO4 motion. The recovery traces K-39, which predominantly undergoes quadrupole relaxation. can be represented by a linear combination of two exponential functions. The temperature dependences of the relaxation rates for K-39 can be described with a simple power law T-1(-1) = alphaT(2). The spin-lattice relaxation rates for the K-39 nucleus in K3H(SO4)(2) and KHSO4 crystals are in accordance with a Ranian process dominated by a phonon mechanism. (C) 2004 Elsevier Ltd. All rights reserved.