The spin-lattice relaxation rates of 35Cl were determined at temperatures of between 200C and the melting point. Upon adding Cu+ (100 to 1000ppm), pronounced maxima were observed in the relaxation rates below the melting point. These were due to a dynamic quadrupole interaction which was caused by the diffusion of the foreign ions. From the diffusion contribution to the relaxation, the mean jump frequencies of the impurities were deduced. These were considerably larger than those of K+ ions (by a factor of 1000 for Cu+ at 500C). The activation energy for Cu+ diffusion was 1.0eV; with a pre-exponential factor of 5 x 1014/s. From a comparison of relaxation measurements in KBr doped with divalent cations, it was concluded that Cu+ was not incorporated at interstitial positions.

Kernresonanz-Untersuchungen zur Diffusion von Cu+ und Anderen Einwertigen Fremdionen in KBr und KCl. K.P.Henke, H.Richtering, U.Ruhrberg: Solid State Ionics, 1986, 21[2], 171-9