Optimization of Pulses with Low Bandwidth for Improved Excitation of Multiple-Quantum Coherences in NMR of Quadrupolar Nuclei

TL;DR

This paper improves NMR pulse optimization for quadrupolar nuclei by using low-bandwidth pulses generated with the GROUP algorithm, leading to better experimental and simulation agreement.

Contribution

It introduces the use of the GROUP algorithm to produce low-bandwidth pulses, addressing phase transient issues in NMR of quadrupolar nuclei.

Findings

GROUP pulses show higher fidelity than GRAPE pulses.

Low-bandwidth pulses reduce phase transient effects.

Enhanced agreement between experimental and simulated NMR results.

Abstract

We discuss the commonly encountered problem when optimizing NMR pulses using optimal control that the otherwise very precise NMR theory does not provide as excellent agreement with experiments. We hypothesize that this disagreement is due to phase transients in the pulse due to abrupt phase- and amplitude changes resulting in a large bandwidth. We apply the GROUP algorithm that gives high fidelity pulses with a low bandwidth compared to the typical GRAPE pulses. Our results obtain a better agreement between experiment and simulations supporting our hypothesis and solution to the problem.