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首页> 外文期刊>Journal of magnetic resonance >Lifetimes of the singlet-states under coherent off-resonance irradiation in NMR spectroscopy
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Lifetimes of the singlet-states under coherent off-resonance irradiation in NMR spectroscopy

机译：核磁共振波谱中相干非共振辐射下单线态的寿命

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摘要

Singlet-states vertical bar S > = (vertical bar alpha beta > - vertical bar beta alpha >)/root 2 can be excited in pairs of coupled spins I and S, first by preparing either a non-vanishing zero-quantum coherence I+S- or a state of longitudinal two-spin order IS. and then by applying a coherent radio-frequency (RF) irradiation with a carrier frequency omega(rf) = (Omega(I) + Omega(S))/2 that lies half-way between the chemical shifts of the two spins involved. The life-times T-S can be much longer than the spin-lattice relaxation time T-1 of longitudinal magnetization, but singlet-states are ultimately relaxed, not only by dipolar interactions between the active spins or with the external spins, but also as a result of a non-vanishing offset Delta omega = omega(rf) - (Omega(I) + Omega(S))/2 or an insufficient amplitude of the RF irradiation that fails to fulfill the condition omega(1) Delta Omega = (Omega(I) - Omega(S)). In this work, the effect of off-resonance irradiation is explored and an approximate formula for the effective relaxation rate of the singlet population is provided on the basis of perturbation theory. The qualitative features of the dependence of the relaxation rate of the singlet population on the offset Delta omega and on the difference Delta Omega of the chemical shifts of the two spins are illustrated by comparison with numerical simulations. (c) 2006 Elsevier Inc. All rights reserved.
机译：单峰态垂直线S> =（垂直线alpha beta>-垂直线beta alpha）/根2可以在成对的自旋I和S中被激发，首先要准备一个不消失的零量子相干I + S轴或纵向两轴顺序IS的状态。然后通过以载波频率omega（rf）=（Omega（I）+ Omega（S））/ 2的相干射频（RF）进行辐射，该频率位于所涉及的两个自旋的化学位移之间。寿命TS可能比纵向磁化的自旋晶格弛豫时间T-1长得多，但是单重态最终得以弛豫，不仅通过主动自旋之间或与外部自旋之间的偶极相互作用，而且失调Δω= omega（rf）-（Omega（I）+ Omega（S））/ 2或RF辐射振幅不足而无法满足条件omega（1） DeltaΩ的结果=（Omega（I）-Omega（S））。在这项工作中，探索了非共振辐射的影响，并基于摄动理论提供了单线态种群有效弛豫率的近似公式。通过与数值模拟的比较，说明了单线态种群的弛豫速率对偏移Δω和两个自旋的化学位移的差Δω的依赖性的定性特征。 （c）2006 Elsevier Inc.保留所有权利。

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