NMR Investigation of the Nitrogen Quadrupole Coupling Constant in Liquid Samples

Nitrogen quadrupole coupling constants have been evaluated for liquid samples from nuclear spin–lattice relaxation time measurements on the basis of a new molecular model. The relaxation times have been determined either from estimates of the magnetic resonance linewidth or by modifications of the progressive-saturation technique. Use of this model requires calculation of an “apparent molecular volume,” which is defined as the volume traced out by those molecular motions contributing to quadrupolar relaxation. Most of the quadrupole constants thereby obtained are in satisfactory agreement with measurements available from the techniques of pure quadrupole resonance and gaseous microwave absorption. When the apparent molecular volume cannot be calculated directly, an estimate of the coupling constant can be obtained from a comparison of molecules with similarly shaped apparent volumes.