脉冲梯度场NMR实验中的弛豫和辐射阻尼效应

RELAXATION AND RADIATION DAMPING EFFECTS IN NMR EXPERIMENES OF PULSED FIELD GRADIENTS

使用梯度脉冲压制水峰已广泛地应用于生物样品的ＮＭＲ实验，一个选择性９０°脉冲接一个纵向的散相梯度脉冲破预期能得到好的去水峰效果．然而基于下面的三方面的原因．梯度脉冲去水峰的效果受到了限制．其一是梯度散相的动力学过程表明总磁化强度的衰减是需要时间的，其二是纵向弛豫Ｔ１机制在梯度脉冲作用过程中不可避免，其三是辐射阻尼效应力图将磁化强度推向ｚ方向．在本文中我们定量地分析了这三种机制在压水峰过程中的作用．

Suppression of water peak with pulsed field gradient has been widely used in NMR experiments of biological samples. p selective 90°pulse followed by a z gradient pulse is expected to result in a good suppression.In this paper,the spin dynamics in the presence of gradient field is quantitatively analyzed,and the longitudinal relaxation and the radiation damping effects during the gradient pulsing are discussed.It is shown that high strength and short duration of the gradient are a choice for better water signal suppression.