Zeeman Effect Study of the Nuclear Quadrupole Resonance of 81Br in 4,4′-Dibromodiphenylether and 4,4′-Dibromodiphenylthioether

The Zeeman effect of the ⁸¹Br NQR line was studied on single crystals of 4,4′‐dibromodiphenylether and 4,4′‐dibromodiphenylthioether. The relative orientations of the electric‐field‐gradient tensors acting upon the Br nuclei in the same molecule have been determined. The angle between the two Z‐axis directions is 129°0′ ± 5′ in the former compound and 107°15′ ± 4′ in the latter. The angle between the normal to the plane determined by the two $Z$ axes in a molecule and the $X$ axis of each gradient is 33°30′ ± 1° and 37°25′ ± 30′, respectively. These values are in general agreement with known data from x‐ray diffraction although the differences are significant. An accurate comparison is not, however, possible since carbon‐atom coordinates are not reported in the literature.