The Zeeman Effect in Quadrupole Double Resonance Spectra: Dependence of the Line Shapes on the Orientation of the Electric Field Gradient Tensor

The solid effect spectrum of 1,4-dichlorobenzene was recorded at magnetic field strengths in excess of 50 G; at these field strengths Zeeman structure is seen on the 35Cl resonance. Unlike in single resonance experiments, peaks are asymmetric, and the high frequency and low frequency solid effect peaks have not the same shape. Computer calculation o f the solid effect spectrum gives peaks which show the same asymmetry as the experimental spectrum. The simulated line shapes are found to depend on the direction the principal components of the electric field gradient in the crystal framework and indicate that qyy lies in the plane o f the benzene ring.