Shrot Yoav, Frydman Lucio
Department of Chemical Physics, Weizmann Institute of Science, 76100 Rehovot, Israel.
J Magn Reson. 2003 Oct;164(2):351-7. doi: 10.1016/s1090-7807(03)00177-0.
Two-dimensional (2D) spectroscopy is central to many contemporary applications of NMR. Recently, we have introduced a new approach whereby 2D NMR spectra can be collected within a single scan. This methodology employs a magnetic field gradient in order to spatially encode the time evolution occurring along the indirect dimension. The discrete nature of the t1 incrementation and its one-to-one correspondence with the spatial encoding, may lead to a number of artifacts. Most notable among these is a periodicity of the spectral peaks that are observed along the indirect axes. The appearance of such 'ghost-peaks', which may sometime coincide with genuine cross-peaks, could hamper a proper interpretation of the spectra. This contribution reviews the origin of such multiple resonances, and proposes a procedure for their elimination based on the acquisition of a small number of complementary scans. Such complementary scans can be simultaneously employed for the sake of phase-cycling out other unwanted signals, and improve the overall indirect-domain spectral resolution. Brief mathematical descriptions of the ghost-peak generation and ghost-peak suppression mechanisms are described, followed by experimental tests on a number of samples using various pulse sequences.
二维（2D）光谱学是许多当代核磁共振应用的核心。最近，我们引入了一种新方法，通过该方法可以在单次扫描中采集二维核磁共振谱。这种方法利用磁场梯度在空间上对沿间接维度发生的时间演化进行编码。t1增量的离散性质及其与空间编码的一一对应关系，可能会导致一些伪影。其中最显著的是沿间接轴观察到的光谱峰的周期性。这种“鬼峰”的出现，有时可能与真实的交叉峰重合，可能会妨碍对光谱的正确解释。本论文回顾了这种多重共振的起源，并提出了一种基于采集少量互补扫描来消除它们的程序。这种互补扫描可以同时用于通过相位循环消除其他不需要的信号，并提高整体间接域光谱分辨率。文中描述了鬼峰产生和鬼峰抑制机制的简要数学描述，随后对一些样品使用各种脉冲序列进行了实验测试。
