Abstract：
The electric field gradient tensor (considered here at the level of a nitrogen nucleus) can be described by two parameters: the largest element in the (X,Y,Z) principal axis system, denoted by VZZ (leading to the nuclear quadrupole coupling), and the asymmetry parameter η = (|VYY| - |VXX|)/|VZZ| with |VZZ| > |VYY| > |VXX|. The frequencies of the three nitrogen-14 nuclear quadrupole resonance (NQR) transitions depend on both parameters but, for sensitivity reasons, their determination may be especially difficult and time consuming. For a partly rigid NH grouping with a labile proton, water nuclear magnetic resonance (NMR) relaxometry curves may exhibit these three transitions (dubbed quadrupolar dips or quadrupole relaxation enhancement (QRE)), provided that the NH grouping belongs to a moiety possessing a sufficient degree of ordering. Their line shape leads to the correlation time describing mainly the motion of the NH grouping (the proton of which being in exchange with water protons), and their amplitude can be interpreted in terms of an effective NH distance. This approach is applied to a hydrogel, where separate NQR lines are observed for the different types of water existing in this system. Furthermore, the analysis of experimental data allows one to determine the nuclear quadrupole coupling in the protonated and deprotonated forms of this molecular moiety involving a labile NH grouping.
摘要：
电场梯度张量（此处在氮核水平上考虑）可以用两个参数来描述：（X，Y,Z)主轴系统,用VZZ表示（导致核四极耦合），和不对称参数η=(|VYY|-|VXX|)/|VZZ|,其中|VZZ|>|VYY|>|VXX|。三个氮14核四极共振（NQR）跃迁的频率取决于两个参数，但是，出于敏感原因，他们的决定可能特别困难和耗时。对于带有不稳定质子的部分刚性NH基团，水核磁共振（NMR）弛豫曲线可能表现出这三个跃迁（称为四极下降或四极弛豫增强（QRE）），条件是NH基团属于具有足够有序程度的部分。它们的线形导致相关时间，主要描述NH基团（其质子与水质子交换）的运动，它们的振幅可以用有效NH距离来解释。这种方法适用于水凝胶，其中对于该系统中存在的不同类型的水观察到单独的NQR线。此外，通过对实验数据的分析，可以确定该分子部分的质子化和去质子化形式的核四极偶合，其中涉及不稳定的NH基团。
