Proton NMR study of the lowest-hydrogen-content molybdenum bronze H0.26MoO3 -: art. no. 144301

Temperature and frequency dependences of proton spin-lattice relaxation time have been measured in the lowest-hydrogen-content molybdenum bronze H0.26MoO3 by pulsed NMR method. Temperature dependence of proton NMR spectra have been also observed. It is revealed that protonic motion becomes active above about 165 K and the fluctuation of dipolar interaction of protons arising from the protonic motion governs the spin-lattice relaxation in the temperature range between 213 and 333 K. The activation energy is determined to be 1.30x10(4) J/mol and the correlation time tau (c) is 1.29x10(-8)s at room temperature. The protonic motion governing the spin lattice relaxation is discussed and it is suggested that the protonic motion is lattice diffusion. The diffusion constant D is estimated to be 3.27x10(-12) m(2)/s.