The enhancement in relaxation of ¹H spins adsorbed at pore walls is well known, described by the famous solutions of Brownstein and Tarr to the Bloch-Torrey diffusion equation with a partially absorbing boundary. Sodium-23 is an alternative nucleus that can be readily accessed at low field, providing a robust discriminator of brine from organic phases in petrophysics and a marker for aqueous ingress in construction materials. We examine NaCl brine in a chalk selected for its monodispersed pore size distribution. The ¹H $T_2$ distribution reflects the pore size distribution as expected. In contrast, the ²³Na $T_2$ distribution is broad and multimodal, consistent with relaxation outside the motional narrowing regime. To understand the ²³Na results, we determine the quadrupole coupling constant QCC and rotational correlation time ${\tau }_{\text{c}}$, and show that well-defined single values of QCC and ${\tau }_{\text{c}}$ describe the observed relaxation behavior. Our observations call for a new interpretation for quadrupole relaxation in pores.

众所周知，通过孔壁上吸附的¹ H自旋的弛豫增强，由Brownstein和Tarr对具有部分吸收边界的Bloch-Torrey扩散方程的著名解进行了描述。钠23是一种可供选择的原子核，可在低场下轻松访问，它提供了岩石物理学中有机相中盐水的强力鉴别剂，并且是建筑材料中水进入的标志物。我们在选择粉笔的NaCl盐水中检查了NaCl盐水的单分散孔径分布。在¹ ^ h${Ť}_{\mathrm{2个}}$分布反映了预期的孔径分布。相比之下，²³ Na${Ť}_{\mathrm{2个}}$分布是广泛的和多峰的，与运动狭窄范围外的放松相一致。要了解²³ Na的结果，我们确定四极耦合常数QCC和旋转相关时间${\tau }_{\text{C}}$，并显示定义明确的QCC和 ${\tau }_{\text{C}}$描述观察到的松弛行为。我们的观察结果要求对孔隙中的四极杆弛豫有新的解释。