Error Compensation without a Time Penalty: Robust Spin-Lock-Induced Crossing in Solution NMR

A modification of the widely used spin-lock-induced crossing (SLIC) procedure is proposed for the solution nuclear magnetic resonance (NMR) of strongly coupled nuclear spin systems, including singlet NMR and parahydrogen-enhanced hyperpolarized NMR experiments. The compensated-SLIC (cSLIC) scheme uses a repetitive sequence where the repeated element employs two different radio-frequency field amplitudes. Effective compensation for deviations in the radio-frequency field amplitude is achieved without increasing the overall duration of the SLIC sequence. The advantageous properties of cSLIC are demonstrated by numerical simulations and representative experiments.