Dynamic and static effects on Cl-35 nuclear quadrupole resonance due to substitutional impurities in crystalline p-dichlorobenzene

The Cl-35 nuclear quadrupole resonance (NQR) spectra of p-dichlorobenzene d oped with p-bromochlorobenzene and p-dibromobenzene have been studied. The measurements were carried out as a function of the concentration up to 10% of impurities and at four temperatures in the 77 K-295 K range. The impurit ies diminish the integrated intensity, shift the peak of the line, and incr ease the linewidth. The frequency of the peak varies linearly with impurity concentration, with a slope depending upon the solute molecule and the tem perature. The increment of the linewidth depends on the solute molecule, bu t not on the temperature. The observed changes of the Cl-35 NQR signal are accounted for by considering the perturbation of the electric field gradien t produced by elastic distortion of the lattice, and by variations in the e lectric charge distribution and phonon spectra.