抄録
The isotropic exchange coupling J and the pseudo-dipolar exchange coupling K between cation and anion nuclear spins and those between cation and cation spins have been determined in single crystals of TlBr and TlCl and TlF powder. The results are given in units of 1022 cm−3: JTl–Br=14, JTl–Tl=38, KTl–Br<5, KTl–Tl<5 for TlBr. Similar, but less complete, data have been obtained in a single crystal of TlCl and TlF powder. The data are compared to indirect spin-spin interactions calculated on an overlap model of Kondo and Yamashita, and the model is found to give reasonably good agreement with the data. However, the predicted spin-spin interaction constants are still too small compared to the data. The predicted chemical shifts on the overlap model are large compared to the experimental values for halogen ions, but too small for thallium ion. The thallium chemical shifts are explained in terms of partial covalent bonding between metal and halogen ions and an average of 3.7 % covalent character per ions is deduced for TlBr.
