Effects of Instrumental Artifacts on Double-Quantum-Filtered NMR Buildup Curves for Spin

We report on the effects of several commonly encountered instrumental artifacts on the buildup curves from a double-quantum-filtered nuclear magnetic resonance (NMR) pulse sequence for spin nuclei. In this work, the artifacts of finite pulse widths, radio frequency field inhomogeneity and pulse transients are studied. The buildup curves are calculated by numerically simulating the evolution of the spin density matrix under the Hamiltonian designed for the artifacts, and are then fit to a bi-exponential equation. The results indicate a clear deviation of the bi-exponential time constants characterizing the buildup curves under certain artifacts, compared with the situation where no artifacts are present. This work shows that the presence of instrumental artifacts may cause a misunderstanding of the buildup curves in experiments, and in turn, the chemical environments that the nuclei experience. We suggest that one optimizes the instruments on certain artifacts before performing the double-quantum-filtered NMR experiments.