Broadband 180 degree universal rotation pulses for NMR spectroscopy designed by optimal control

TL;DR

This paper introduces a new method for designing broadband 180-degree universal rotation pulses in NMR spectroscopy using optimal control, offering improved performance and robustness over traditional composite pulses.

Contribution

The paper presents a novel optimal control approach for creating broadband universal rotation pulses that outperform existing composite schemes, especially in RF inhomogeneity tolerance.

Findings

Designed pulses show improved robustness to RF inhomogeneity.

Applicable to Carbon-13 spectroscopy on common probes.

Modified algorithms incorporate symmetry and relax peak RF limits.

Abstract

Broadband inversion pulses that rotate all magnetization components 180 degrees about a given fixed axis are necessary for refocusing and mixing in high-resolution NMR spectroscopy. The relative merits of various methodologies for generating pulses suitable for broadband refocusing are considered. The de novo design of 180 degree universal rotation pulses using optimal control can provide improved performance compared to schemes which construct refocusing pulses as composites of existing pulses. The advantages of broadband universal rotation by optimized pulses (BURBOP) are most evident for pulse design that includes tolerance to RF inhomogeneity or miscalibration. We present new modifications of the optimal control algorithm that incorporate symmetry principles and relax conservative limits on peak RF pulse amplitude for short time periods that pose no threat to the probe. We apply them to generate a set of pulses suitable for widespread use in Carbon-13 spectroscopy on the majority of available probes.