Dvinskikh Sergey V, Sandström Dick
Division of Physical Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden.
J Magn Reson. 2005 Jul;175(1):163-9. doi: 10.1016/j.jmr.2005.03.016. Epub 2005 Apr 22.
The popular PISEMA experiment is highly sensitive to the 1H chemical shift dispersion and the choice of the 1H carrier frequency. This is due to the off-resonance 1H irradiation in the FSLG-CP sequence employed during the dipolar evolution period. In the modified approach described in this work, the interfering frequency offset terms are suppressed. In the new pulse schemes, conventional FSLG-CP is intercalated with 180 degrees pulses applied simultaneously to both frequency channels, and with phases set orthogonal to those of the spin-lock fields. The technique is demonstrated on a nematic liquid-crystalline sample. Extensions to amplitude-modulated FSLG-CP recoupling under MAS are also presented.
广受欢迎的PISEMA实验对1H化学位移分散和1H载波频率的选择高度敏感。这是由于在偶极演化期采用的FSLG-CP序列中存在失谐1H辐照。在本工作中描述的改进方法中，干扰频率偏移项被抑制。在新的脉冲序列中，传统的FSLG-CP穿插有同时施加到两个频率通道的180度脉冲，且相位设置为与自旋锁定场的相位正交。该技术在向列型液晶样品上得到了验证。还介绍了在MAS下对幅度调制FSLG-CP重新耦合的扩展。
