Anomaly of Nuclear Quadrupole Relaxation in Cu20 Prepared at Low Temperatures*

The 63Cu and 65Cu NQ R transitions in powder samples o f cuprous oxide have been in­ vestigated from 77 to 500 K and at room temperature after annealing up to 1100 K Significant differences in T \ , NQ R linewidth A v, and their temperature dependences were found among the samples prepared in different ways. For Cu20 samples obtained in low temperatures (below 380 K), the temperature dependence o f T\ below 380 K is o f activation character with Ea = 0.07 eV. These results are interpreted in terms o f an electron hopping mechanism. Thermal processing o f these samples permits to obtain irreversible electronic state and then the spectroscopic parameters are the same as for the samples obtained in high temperatures (above 1320 K).