Powder Zeeman NQR (PZNQR) spectra of 63Cu,75As, and 35Cl in various compounds have been observed at 77 K. On the basis of the types of simulated integral curves of PZNQR absorption, the estimated asymmetry parameters of the electric field gradients have been divided into three classes; (1) measurable, (2) small (smaller than about 0.05), and (3) very small (probably zero). The asymmetry parameters have been found to be very small ( Cu, NQR frequency = 26.704 MHz) in Cu,0;0.40 (63Cu, 32.617 MHz) in KCu(CN)2; very small (75As, 116.820 MHz) in As2O3 ; very small (75As, 78.950 ; 35Cl, 25.0567 and 25.4036 MHz) and small ( 35Cl, 24.9581 MHz) in ASCl3 ; very small (75As, 98.501 and 99.046 MHz) in As(C6H5)3; small (38.389 MHz), 0.15 (38.464 MHz), and 0.14 ( 38.503 MHz) for 35Cl in hexachlorobenzene; small ( 35.847 MHz) and very small ( 39.154,39.603 , and 39.615 MHz) for 35Cl in l-chloro-2-(trichloromethyl)-benzene; small ( 32.619 MHz) and very small ( 32.878 MHz) for 35Cl in 1,4-dichlorobutane; very small ( 37.828 and 38.051 MHz) for 35Cl in 1,1,1 -trichloroethane.

The structures of α-antimony tribromide and its molecular complex with benzene 2SbBr3·C6H6 were investigated by studying the Zeeman effect on the nuclear quadrupole resonance (NQR) due to 81Br at room temperature. The bond angles, ∠Br-Sb-Br, of α-antimony tribromide in its solid state were found to be 94°14±4′, 94°31′±8′, and 98°27′±7′. The polar angles specifing the directions of the Sb-Br bonds with respect to the orthorhombic crystal axes are (60°0′±9′, 62°13′±7′), (59°10′±7′, −54°35′±8′), and (57°39′±17′, 180°0′±3′). These values are consistent with those of the X-ray analysis by Gushen et al. within about 1°. The asymmetry parameters at the three bromine atoms were 0.068±0.002, 0.049±0.002, and 0.080±0.004. On the other hand, the bond angles, ∠Br-Sb-Br, of the SbBr3 molecule in the complex 2SbBr3·C6H6 were found to be 92°24′±11′, 97°7′±14′, and 97°40′±6′. The crystal has a monoclinic symmetry, and the three Sb-Br bonds have directions making angles of 29°4′±21′, 76°26′±9′ and 63°33′±11′ relative to the b-axis. The asymmetry parameters at the three bromine atoms in the complex were 0.169±0.001, 0.063±0.002, and 0.094±0.002. The largest value of the asymmetry parameters seems to be the result mostly of the intermolecular bonding. From the coupling constants, the Sb-Br bond characteristics in antimony tribromide and its molecular complex, 2SbBr3·C6H6, are considered to be almost the same.

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The Zeeman NQR of 79 Br and 81 Br in samples having relatively small r\ was studied on several bromine compounds which were in the powder or polycrystal state. The absorption lines were detected in the integral form by the bridge circuit. When a static magnetic field was applied, the line shapes were broadened and usually two dips appeared symmetrically at both sides of the zero field line. The values of rj were estimated from the patterns of the dips. For compounds such as NaBr0 3 , however, as expected no dips were observed.

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