Kasumaj B, Stoll S
Laboratory of Physical Chemistry, ETH Zurich, 8093 Zurich, Switzerland.
J Magn Reson. 2008 Feb;190(2):233-47. doi: 10.1016/j.jmr.2007.11.001. Epub 2007 Nov 6.
In 3-pulse ESEEM and the original 4-pulse HYSCORE, nuclei with large modulation depth (k approximately 1) suppress spectral peaks from nuclei with weak modulations (k approximately 0). This cross suppression can impede the detection of the latter nuclei, which are often the ones of interest. We show that two extended pulse sequences, 5-pulse ESEEM and 6-pulse HYSCORE, can be used as experimental alternatives that suffer less strongly from the cross suppression and allow to recover signals of k approximately 0 nuclei in the presence of k approximately 1 nuclei. In the extended sequences, modulations from k approximately 0 nuclei are strongly enhanced. In addition, multi-quantum transitions are absent which simplifies the spectra. General analytical expressions for the modulation signals in these sequences are derived and discussed. Numerical simulations and experimental spectra that demonstrate the higher sensitivity of the extended pulse sequences are presented.
在三脉冲电子自旋回波包络调制（ESEEM）和原始的四脉冲高分辨超精细结构（HYSCORE）中，具有大调制度（k约为1）的核会抑制来自调制度较弱（k约为0）的核的光谱峰。这种交叉抑制会妨碍对后一种核的检测，而这些核往往是我们感兴趣的。我们表明，两种扩展脉冲序列，即五脉冲ESEEM和六脉冲HYSCORE，可以用作实验替代方案，它们受交叉抑制的影响较小，并且在存在k约为1的核的情况下能够恢复k约为0的核的信号。在扩展序列中，来自k约为0的核的调制被大大增强。此外，不存在多量子跃迁，这简化了光谱。推导并讨论了这些序列中调制信号的一般解析表达式。给出了数值模拟和实验光谱，证明了扩展脉冲序列具有更高的灵敏度。
