High Sensitivity Nuclear Quadrupole Resonance of Light Nuclei

Nuclear quadrupole resonance (NQR) is the study of the energy splittings due to interaction of the electric quadrupole moment of the nucleus with the electric field gradient that exists at the nuclear site. Many nuclei with spins greater than Vz have a quadrupole moment and most of these quadrupole moments have been measured and tabulated. Thus, the information gained by studying NQR is the magnitude, orientation, and symmetry of the electric field gradient at the nuclear site. In general, the electric field gradient may be expressed in a set of axes (oxyz) as a collection of nine second derivatives of the electrostatic potential V, such as Vxx = d2VIddx , VXY = d'Vldxdy etc. As with moments of inertia, it is possible, by choosing a particular set of axes {OXYZ), called the principal axes, to reduce these nine parameters to three, namely Vxx, VYY, and Vzz. Even these three parameters are not independent as, in a region of no charge, the Laplace equation A V = 0 demands that