Continuous-wave and pulsed-EPR study of theCu2+65-doped NaOD-water system in the amorphous and polycrystalline phases

Frozen aqueous solutions of sodium hydroxide doped with a small amount of paramagnetic ${}_{}{}^{65}{}_{}{}^{}\mathrm{Cu}_{}^{2+}{}_{}{}^{}$ ions have been investigated in the amorphous and polycrystalline phases by means of continuous-wave and pulsed-electron-paramagnetic-resonance spectroscopy. The continuous-wave spectra of the amorphous phase recorded at 77 K showed a significant g and A strain if compared to that of the polycrystalline phase, indicating random distortions of the local environment of the paramagnetic ions. On the other hand, spin-lattice relaxation rates obtained from magnetization-recovery data, put into evidence dynamical anomalies typical of the glassy state of matter. The low-temperature (from 2 to 5 K) behavior of the relaxation rates in the amorphous phase is consistent with the existence of two-level states coupled to the paramagnetic centers, while the behavior of the Raman relaxation process (from 5 to 100 K) indicates an anomaly in the density of vibrational states, probably due to mode-localization phenomena.