The nuclear quadrupole moment mesured with Nuclear Quadrupole Resonance   NQR : Principle and definition
  The nuclear quadruple moment is a fundamental character associated to the nuclei, this moment is related to the not purely spherical distribution in the nuclei, indeed its measure allows us to survey the geometric deformation of the nuclei of its spherical shape. The measurement methods of the quadruple moment is to study the electrical energy hyperfine interaction between the quadruple moment and the electric field gradient due to atomics electrons, one of the methods is the nuclear quadruple resonance NQR which is observed at the transitions between energy levels splits by the effect of the quadruple interaction and induced by a radio frequency field. 
Mohamed Belfkir
nucl-th