1H nuclear magnetic resonance and Gd3+ electron spin resonance studies of water molecular and electron spin dynamics in Sm(NO3)3•6H2O

The H-1 nuclear magnetic resonance (NMR) spin-lattice relaxation time (TI), the spin-lattice relaxation time in a rotating flame (T-1p), Gd3+ electron spin resonance (ESR) spectra and differential thermal analysis (DTA) were measured for Sm(NO3)(3). 6H(2)O. A new thermal anomaly was detected by DTA at 183 K during the heating process. The temperature dependence of TI, could be explained by the motion of four kinds of water molecule. The activation energies and the correlation times at infinite temperature for each water molecule were estimated from T-1p. In phase III, hysteresis of T-1p, which is considered to be caused by the crystallization water molecules, was observed. From the results of H-1-NMR T-1 and doped Gd3+ ESR spectra, the electron spin-lattice relaxation of Sm3+ proved to be dominated by the Orbach process which occurs through the second excited state caused by the crystal field. (C) 1998 Elsevier Science Ltd. All rights reserved.