Accessories for low-frequency hyperpolarized xenon pulsed NMR

核磁共振是一种非常强大的分析工具，广泛应用于物理、化学、工程、生物和医学等领域。尽管核磁共振在技术和科学上具有重要意义，但由于核自旋可以极化的比例相对较小，即使在超导磁体产生的大磁场存在的情况下，常规核磁共振也存在灵敏度低的问题。近年来，人们已经证明了用强激光的方法可以在氙气中实现高自旋极化。然后，超极化的氙气可以用作需要高灵敏度和/或空间选择性的新型核磁共振实验中的磁性探针。我们正在寻求一种这样的应用，即固体样品表面的增强型固态核磁共振波谱。超极化磁探针的另一个优点是，可以在不使用昂贵的超导磁体的低磁场中进行具有可接受信噪比的实验。在这里，我们正在为一些次要但必不可少的部件寻求资金，以完成我们生产超极化氙气并用它来表征固态表面的设备。我们正在申请资助的一些项目将用于表征和优化在连续流动自旋交换光学偏振器中产生的氙气的核自旋极化、弛豫时间和产生率。剩下的项目是组装一个低频(100 kHz-1 MHz)脉冲核磁共振系统，用于千古斯场的光谱分析，我们将使用非超导螺线管产生该系统。我们将用这个低场设备进行的第一个实验是对高温超导体表面涡旋相的超极化氙气核磁共振研究。

Nuclear magnetic resonance (NMR) is an extremely powerful analytical tool used in the fields of physics, chemistry, engineering, biology and medicine. Despite its technological and scientific importance, conventional NMR suffers from low sensitivity arising from the relatively small percentage of nuclear spins that can be polarized, even in the presence of large fields generated by superconducting magnets. In recent years it has been demonstrated that high-spin polarization may be achieved in xenon gas by a method employing intense lasers. The hyperpolarized xenon may then be used as a magnetic probe in novel NMR experiments requiring high sensitivity and/or spatial selectivity. We are pursuing one such application, namely, enhanced solid-state NMR spectroscopy of solid sample surfaces.Another advantage of a hyperpolarized magnetic probe is that experiments having acceptable signal to noise ratios may be performed in low magnetic fields that are attainable without the use of costly superconducting magnets. Here we are seeking funding for a few minor but essential components to complete our apparatus for producing hyperpolarized xenon and using it to characterize solid-state surfaces. Some items for which we are requesting funding will be used to characterize and optimize the nuclear-spin polarization, the relaxation times, and the production rate of xenon produced in a continuous-flow spin-exchange optical polarizer. The remaining items are for assembly of a low-frequency (100 kHz-1 MHz) pulsed NMR system for spectroscopy at kilogauss fields, which we will generate using a non-superconducting solenoid. The first experiment we will perform with this low-field apparatus is a hyperpolarized xenon-NMR study of the vortex phase at the surface of a high-temperature superconductor.