Leskes Michal, Madhu P K, Vega Shimon
Department of Chemical Physics, Weizmann Institute of Science, Rehovot 76100, Israel.
J Chem Phys. 2006 Sep 28;125(12):124506. doi: 10.1063/1.2352737.
We present here a bimodal Floquet analysis of the windowed phase-modulated Lee-Goldburg (wPMLG) sequence for homonuclear dipolar decoupling. One of the main criteria for an efficient homonuclear dipolar decoupling scheme is an effective z-rotation condition. This is brought about by the presence of radio-frequency imperfections in the pulse sequence together with a systematic manipulation of the wPMLG pulses. Additional improvement in the (1)H spectral resolution was obtained by a proper understanding of the off-resonance dependence of the wPMLG irradiation scheme based on bimodal Floquet theory. Numerical investigations further corroborate both theoretical and experimental findings. Theoretical analysis points to accidental degeneracies between the cycle time of the wPMLG sequence and the rotor period leading to the experimentally observed off-resonance dependence of the resolution. Two-dimensional (1)H-(1)H homonuclear single-quantum correlation spectra of model amino acids are also presented, highlighting the improved spectral resolution of wPMLG sequences.
我们在此展示了用于同核偶极去耦的加窗相位调制Lee-Goldburg（wPMLG）序列的双峰弗洛凯分析。高效同核偶极去耦方案的主要标准之一是有效的z旋转条件。这是由脉冲序列中射频缺陷的存在以及对wPMLG脉冲的系统操纵所导致的。通过基于双峰弗洛凯理论正确理解wPMLG辐照方案的失谐依赖性，获得了（1）H谱分辨率的进一步提高。数值研究进一步证实了理论和实验结果。理论分析指出，wPMLG序列的循环时间与转子周期之间存在偶然简并，导致实验观察到的分辨率的失谐依赖性。还展示了模型氨基酸的二维（1）H-（1）H同核单量子相关谱，突出了wPMLG序列改善后的谱分辨率。
