Nuclear relaxation processes of paramagnetic complexes The slow-motion case
Nuclear relaxation processes of paramagnetic complexes The slow-motion case
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顺磁配合物的核弛豫过程 慢动作情况
DOI：
10.1080/00268977600100261
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发表时间：
1976
影响因子：
1.7
通讯作者：
D. Fiat
中科院分区：
文献类型：
--
作者：
A. J. Vega;D. Fiat
翻滚顺磁分子中的核弛豫机制是两个过程的叠加，通常的“S-机制”和附加的“χ-机制”。后者由电子自旋极化的热平均引起，并方便地用分子磁化率χ来描述。导出了由于χ松弛引起的T1和T2的表达式。在转动相关时间比电子自旋弛豫时间长四个数量级的情况下，χ-贡献是可观的。χ-弛豫速率随外场的增加呈二次方增加。各向异性磁化率和化学交换的影响被认为是。它表明，在某些重要的情况下，N.M.R.即使当化学交换速率比翻滚速率快得多时，线宽也不由化学交换速率决定。
The nuclear relaxation mechanism in tumbling paramagnetic molecules is a superposition of two processes, the usual ‘S-mechanism’ and an additional ‘χ-mechanism’. The latter arises from the thermal average of the electron spin polarization and is conveniently described in terms of the molecular susceptibility χ. Expressions for T 1 and T 2 due to χ-relaxation are derived. The χ-contribution is appreciable in cases where the rotational correlation time is four orders of magnitude longer than the electron spin relaxation time. The χ-relaxation rates increase quadratically with the external field. The effects of anisotropic susceptibility and of chemical exchange are considered. It is shown that in certain important cases the N.M.R. line width is not determined by the chemical exchange rate, even when it is much faster than the tumbling rate.