Zeeman Splitting of Nuclear Quadrupole Resonance in Paradibromobenzene

Abstract

Zeeman patterns of the nuclear quadrupole resonance line of Br ⁷⁹ were studied with a single crystal of paradibromobenzene. The crystal contains two classes of molecules with equal positive and negative inclinations against the crystallographic b -axis. Changing the orientation of magnetic field in the plane perpendicular to the b -axis, the Zeeman patterns were measured. The asymmetry parameter of the coupling, η, was determined from the pattern at the magnetic field perpendicular to all carbon-brormine bonds. The result was η=0.12±0.01. The coupling constant, e Q q , was measured as 535.19 Mc at 14°C. If the asymmetry parameter is completely due to the resonance of a double bond structure in the carbon-bromine bond, the observed value gives 4.5 per cent double bond character.