Influence of the Overhauser effect on 14N PNQR T1 measurements on a single crystal of parachloroaniline

Abstract

Spin lattice relaxation measurements of ¹⁴N by PNQR pulse experiments on a single crystal and powder of parachloroaniline are reported. In this compound, there are two symmetry related nitrogen sites in the unit cell. The dipolar interaction between nuclei in both sites affects the experimental results by an Overhauser‐type effect. This effect on various types of pulse experiments is analyzed. To simplify the analysis, the quadrupole Hamiltonian is expressed in terms of fictitious spin 1/2 angular momentum operators. The density matrix in this representation in the rotating frame of the quadrupole Hamiltonian is discussed, and the signal function for various types of pulse experiments is derived. The experimental results are in good agreement with theory.