Evolution of magnetization in aB1 field. I. The impact ofB0/B1 inhomogeneity and fast chemical exchange in high-resolution NMR
✍ Scribed by Sz�ntay, Csaba
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 460 KB
- Volume
- 11
- Category
- Article
- ISSN
- 1043-7347
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✦ Synopsis
Since the classical treatment by Torrey in 1949 of the problem of how magnetization evolves in a continuously applied B radiofrequency field, the topic has 1 received relatively little attention in the nuclear magnetic resonance literature. This article focuses on the behavior of the macroscopic magnetization as well as that of its isochromatic constituents in both ''hard'' and ''soft'' resonant B fields by examining the effects of B and 1 0 B inhomogeneities and moderately fast chemical exchange. Discussion embraces the 1 out-of-coil regions where spins experience large B inhomogeneity and give, under suitable 1 conditions, well-detected signals. It is shown that the effect of ⌬ B inhomogeneity is 1 formally similar to increased transverse decay and longitudinal recovery rates in a homogeneous B field, and can lead to two different types of transient phase randomization of 1 isochromatic net magnetizations, which in turn give different macroscopic behaviors. Some practical implications relating to these considerations are also noted.