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

The spin–lattice relaxation rates for 1H and 39K 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 1H can be represented for both crystals with a single exponential function, but cannot be represented by the Bloembergen–Purcell–Pound (BPP) function, so is not related to HSO4 motion. The recovery traces of 39K, which predominantly undergoes quadrupole relaxation, can be represented by a linear combination of two exponential functions. The temperature dependences of the relaxation rates for 39K can be described with a simple power law T1−1=αT2. The spin–lattice relaxation rates for the 39K nucleus in K3H(SO4)2 and KHSO4 crystals are in accordance with a Raman process dominated by a phonon mechanism.