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By35 C1 NQR the temperature dependences of the resonance frequencies and spin4attice relaxation times for the 35 C1 nuclei have been studied in solid CCl 3 COHal (Hal = F, CI, Br, I). A linear correlation between the average 35 C1 NQR frequencies of the CC1 3 groups and the electronegativities of the halogen atoms in the COHal groups has been discovered. The temperature-dependent NQR data reveal thermoactivated reorientations of the CCl 3 COHal molecules as a whole in the crystal lattice. The activation energies of this motion are found to lie in the range 31 -37 kJ mol

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Several experimental techniques have shown evidence for the existence of internal magnetic fields of the order of 200 G in oc-Bi20 3 [1]. The asymmetrical 209Bi N Q R lineshapes in Bi30 4Br also point to a source of poorly resolved splitting present in this compound.In order to obtain further insight into the origin of the local magnetic fields in these compounds the 209Bi N Q R lineshapes of polycrystalline a-Bi20 3 and Bi30 4Br were recorded in weak (below 500 G) static magnetic fields. A calculation of the expected powder lineshapes in a-Bi20 3 under the influence of the internal and applied magnetic fields up to 1 kG was made. The results of the computer simulation are compared with the lineshapes recorded. From the 209Bi lineshapes ob served in the experiment, the local magnetic field at one of the two Bi-sites in Bi30 4Br was estimated.

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