Proton magnetic relaxation study of molecular reorientation in NH4ReO4

摘要: Abstract Measurements of the proton T 1 , ρ and 1D in NH 4 ReO are reported as a function temperature over range from 60 to 300 K. The dependence can be described terms dipolar interaction between protons within an + ion made time dependent by rapid classical reorientation at rate which may Arrhenius relation. activation energy for molecular is 2.2 kcal mole −1 . Over limited regions this same model also used explain results. However, low temperatures data suggest importance quantum mechanical tunneling, high coupling rhenium spins rendered spin-lattice relaxation dominates both Due strong angular rates associated with proton-rhenium interaction, nonexponential decays occur powdered sample these experiments. From results it concluded that dominated quadrupolar Raman spin-phonon interaction. There no evidence any measurements previously postulated order-disorder phase transition vicinity 200 K involving ions.