RELAXATION DURING ADIABATIC RADIOFREQUENCY PULSES

这个子项目是许多研究子项目中的一个 由NIH/NCRR资助的中心赠款提供的资源。子项目和 研究者（PI）可能从另一个NIH来源获得了主要资金， 因此可以在其他CRISP条目中表示。所列机构为 研究中心，而研究中心不一定是研究者所在的机构。 在这项工作中，我们处理的绝热射频脉冲过程中的松弛的一般问题。在NMR文献中，RF脉冲期间的弛豫被忽略或使用所谓的“δ函数近似”来避免，其中假设脉冲的短时间期间的弛豫是可忽略的。 然而，使用持续时间在许多毫秒量级的RF脉冲变得越来越普遍，其中在第一旋转帧中存在明确的时间依赖性。这些发展的结果是，RF脉冲期间的弛豫时间依赖性对于NMR数据的成功分析变得重要。在这项工作中，我们详细介绍了一些理论概念治疗NMR弛豫，我们已经发现有必要在开发成功的拟合数据的NMR实验中的时间依赖性的结果从使用绝热脉冲。我们明确地对待相同的自旋<$$>的情况下，然后两个不同的自旋<$<$的情况下的偶极弛豫机制和两个网站的化学交换。

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. In this work, we treat the general problem of relaxation during an adiabatic radiofrequency pulse. In the NMR literature, relaxation during a RF pulse has either been neglected or avoided using the so-called "delta function approximation" where relaxation during the short time of the pulse is assumed to be negligible. However, it is becoming more and more common to use RF pulses having durations on the order of many milliseconds, where there is an explicit time-dependence in the first rotating frame. The result of these developments is that the time-dependence of relaxation during the RF pulse becomes important for the successful analysis of NMR data. In this work we detail some of the theoretical concepts for treating NMR relaxation that we have found necessary in developing the successful fitting to data of NMR experiments where the time dependence results from the use of adiabatic pulses. We explicitly treat the case of identical spins ¿, then the situation of two distinct spins ¿ both for the case of the dipolar relaxation mechanism and for two site chemical exchange.