The temperature-dependence of the electron-spin-lattice-and -spin-spin-relaxation times T, and T, of Cu(I1) in (Tetrabutyl-ammonium)-Ni(II)bis(l, l-dicyanoethylene-2,2-dithiolate) single crystals are reported. In the range of the direct processes (T = 2. --7OK) a dependence of the spinlattice relaxation rate on the orientation of the Cu-nuclear spin waa observed. From the temperature-dependence of the RAMAN-process the DEBYE-temperature and the averaged soundvelocity of the molecular crystal have been derived being 0 = (100 -f 10)"K and
A general formula is derived for the direct spin-lattice relaxation process of paramagnetic ions with 8 = +for arbitrary orientations of an external magnetic field relative to the crystal axes. Using the formula obtained, Tl of Cuzt ions in square planar coordination geometries is calculated in the point charge approximation. The temperature, concentration, and angular dependence of TI of Cu2+ ions in Ni(II)bis(diethyl-dithiocarbamate) single crystals are reported. Including some features of covalency a reasonable agreement between the theoretical and experimental values of T, is reached. Es wird von detaillierten Untersuchungen zur Temperatur-, Konzentrations-und Winkelabhingigkeit der Spin-Gitter-Relaxationszeit TI von Cutt -1onen in Ni(II)bis(diLthyldithiocarbamat)-Einkristallen berichtet. Fur den direkten RelaxationsprozeB von paramagnetischen Ionen mit S = -:wird eine allgemeine Beziehung abgeleitet, die die Berechnung von T, fur beliebige Magnetfeldorientierungen gestattet. Ausgehend von dieser Beziehung wird die Berechnung von T, fiir Cii2+-Ionen in quadratisch planaren Koordinationsgeometrien im Rahmen der Kristallfeldtheorie beschrieben. Die teilweise Berucksichtigung der Kovalenz fuhrt zu einer verniinftigen tfbereinstimmung mit den experimentellen Daten.
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