Coherence locking in a parallel nuclear magnetic resonance probe defends against gradient field spillover.

Abstract

The implementation of parallel nuclear magnetic resonance detection aims to enhance measurement throughput in support of high-throughput-screening applications, including, for example, drug discovery. In support of modern pulse sequences and solvent suppression methods, each detection site must have independent pulsed field gradient capabilities. Hereby, a challenge is introduced in which the local gradients applied in parallel detectors introduce field spillover into adjacent channels, leading to spin dephasing and, hence, to signal suppression. This study proposes a compensation scheme employing optimized pulses to achieve coherence locking during gradient pulse periods. The design of coherence-locking pulses utilizes optimal control to address gradient-induced field inhomogeneity. These pulses are applied in a pulsed-gradient spin echo (PGSE) experiment and a parallel heteronuclear single quantum coherence (HSQC) experiment, demonstrating their effectiveness in protecting the desired coherences from gradient field spillover. This compensation scheme presents a valuable solution for magnetic resonance probes equipped with parallel and independently switchable gradient coils.