Zeeman Effect of the Nuclear Quadrupole Resonance Spectrum in Crystalline Powder

The Zeeman effect of the nuclear quadrupole resonance spectrum for spin I=32 in crystalline powder has been studied. Theoretical considerations have predicted that, in a nonaxial electric field gradient, the absorption line should be broadened with a characteristic envelope by a weak static magnetic field. When a radio-frequency (rf) field is applied parallel to the static field, one pair of sharp minima should be produced on the envelope at the frequencies shifted by ±γH/2π from the unperturbed quadrupole resonance line, and two pairs of sharp maxima at ±(1−η)γH/2π and at ±(1+η)γH/2π. Resonance spectra of Cl35 nuclei in p-dichlorobenzene and cyanuryl chloride have clearly displayed the predicted shape of envelopes on a recorder at room temperature. Analysis of them has resulted in determining the asymmetry parameters of electric field gradients with considerable accuracy; 0.070±0.01 for the α-modification of p-dichlorobenzene, and 0.22±0.03 for ν1 line, and 0.23±0.04 for ν2 line of cyanuryl chloride.