Clean Absorption‐Mode NMR Data Acquisition

Multi-dimensional Fourier Transform (FT) NMR spectroscopy is broadly used in chemistry[1] and spectral resolution is pivotal for its performance. Phase-sensitive, pure absorption mode signal detection[1a,2] is required for achieving high spectral resolution since an absorptive signal at frequency Ω0 rapidly decays proportional to 1/(Ω0-Ω)2 while a dispersive signal slowly decays proportional to 1/(Ω0-Ω). Hence, a variety of approaches were developed to accomplish pure absorption mode signal detection.[1a,2] Moreover, by use of techniques such as spin-lock purge pulses[3], phase cycling,[1a] pulsed magnetic field gradients,[4] or z-filters,[5] radio-frequency (r.f.) pulse sequences for phase-sensitive detection are designed to avoid ‘mixed’ phases, so that only phase errors remain which can then be removed by a zero- or first-order phase correction.