With the development of sophisticated pulsed field gradient- and phase cycling-approaches for suppressing certain coherence transfer pathways and selecting for others it is sometimes easy to forget that the process is not flawless. In some cases artifacts can emerge because unwanted transfers are immune to the phase cycle or the application of gradients. We consider here a simple ¹H,¹³C HMQC pulse scheme and show that imperfections in the single ¹H 180° refocusing pulse can give rise to small artifacts in methyl spectra that cannot be eliminated through extensive phase cycling or the use of gradients, but that are easily removed when the pulse is of the composite variety.

随着复杂的脉冲场梯度和相位循环方法的发展，用于抑制某些相干传递路径并选择其他相干路径，有时很容易忘记该过程并非完美无缺。在某些情况下，可能会出现伪影，因为不需要的传输不受相周期或梯度施加的影响。我们在这里考虑一个简单的¹ H，¹³ C HMQC脉冲方案，并表明单个¹ H 180°重聚焦脉冲中的缺陷会引起甲基光谱中的小伪影，这些伪影无法通过广泛的相位循环或使用梯度来消除，但是当脉冲为复合类型时，很容易将其清除。