An alternative tuning approach to enhance NMR signals
An alternative tuning approach to enhance NMR signals
复制标题
DOI：
10.1016/j.jmr.2008.04.026
复制
发表时间：
2008-07-01
影响因子：
2.2
通讯作者：
Desvaux, Herve
中科院分区：
文献类型：
--
作者：
Marion, Denis J. -Y.;Desvaux, Herve
通过使用自旋噪声型测量，我们表明经典 NMR 波谱仪接收电路的谐振频率与拉莫尔频率不匹配，即使在发射时电子电路完美调谐在拉莫尔频率并与放大器阻抗匹配。我们还表明，这种自旋噪声方法可用于确保拉莫尔频率与接收电路谐振频率之间的匹配。在这些条件下，(i) 辐射阻尼场与磁化强度完全正交，并且 (ii) NMR 信号水平和潜在的信噪比得到增强。对于 500 或 700 MHz 光谱仪，这种选择会导致探头共振频率发生数百 kHz 的变化。我们表明，可以通过添加位于激励线上（或通过接收线上的对称性）的其他调谐和匹配自由度来消除由此产生的发射失配条件，这些自由度通过交叉二极管与探针谐振电路解耦。 (c) 2008 Elsevier Inc. 保留所有权利。
By using spin-noise type measurement we show that the resonance frequency of the reception circuit of classical NMR spectrometers does not match the Larmor frequency even if, in emission, the electronic circuit is perfectly tuned at the Larmor frequency and matches the amplifier impedance. We also show that this spin-noise method can be used to ensure a match between the Larmor frequency and the reception circuit resonance frequency. In these conditions, (i) the radiation damping field is in perfect quadrature to the magnetization and (ii) the NMR signal level and potentially the signal-to-noise ratio, are enhanced. This choice induces a change of the probe resonance frequency by several hundreds of kHz for 500 or 700 MHz spectrometer. We show that the resulting mismatch condition for emission can be removed by adding other tuning and matching degrees of freedom located on the excitation line (or by symmetry on the reception line) decoupled to the probe resonance circuit by the crossed diodes. (c) 2008 Elsevier Inc. All rights reserved.