弱耦合自旋1/2二核系统二维动态NMR谱

二维动态NMR谱通常可由三脉冲实验得到。但如果核系统有标量耦合,就有可能混淆实验所得的信息。本文在Liouvelle空间中求出二核弱耦合系统的二维理论动态谱,给出AX(I=1/2)系统中的密度矩阵的解析解。文中指出:(1)在梯度脉冲作用之后,密度矩阵将留下z分量、零量子相干和双量子相干。(2)标量耦合与交换作用、弛豫作用的影响不同。前者只对零量子相干及双量子相干有贡献。如果实验得当,有希望消除标量耦合对动态谱的干扰。 关键词：

TWO DIMENSIONAL DYNAMICAL NMR SPECTRUM IN WEAK COUPLED TWO SPIN (I=l/2) SYSTEM

In general, two dimensional dynamic NMR spectrum can be obtained by means of three-pulses experiment. But the informations from this experiment may sometimes be obscured if the scalar coupling in the nuclear system appears. In this work, a theoretical 2D dynamic NMR spectrum of weak coupled two spin system is calculated in Liouvelle space. The analytic solutions of density matrix in AX(I=1/2) system is given. It is shown that (1) after applying of gradient pulse, a z-component, a zero-quantum coherence and a double-quantum coherence will be left in the density matrix; (2) the effects of scalar coupling is different from those of exchange and relaxation and the former only contributes to the zero-quantum coherence and double-quantum coherence. Therefore, one can expect that the interference from the scalar coupling would be eliminated in some appropriate experiment.