Han S, Kühn H, Häsing F W, Münnemann K, Blümich B, Appelt S
Max-Planck Institute for Polymer Research, Ackermannweg 10, D-55128, Mainz, Germany.
J Magn Reson. 2004 Apr;167(2):298-305. doi: 10.1016/j.jmr.2004.01.004.
We have visualized the melting and dissolution processes of xenon (Xe) ice into different solvents using the methods of nuclear magnetic resonance (NMR) spectroscopy, imaging, and time resolved spectroscopic imaging by means of hyperpolarized 129Xe. Starting from the initial condition of a hyperpolarized solid Xe layer frozen on top of an ethanol (ethanol/water) ice block we measured the Xe phase transitions as a function of time and temperature. In the pure ethanol sample, pieces of Xe ice first fall through the viscous ethanol to the bottom of the sample tube and then form a thin layer of liquid Xe/ethanol. The xenon atoms are trapped in this liquid layer up to room temperature and keep their magnetization over a time period of 11 min. In the ethanol/water mixture (80 vol%/20%), most of the polarized Xe liquid first stays on top of the ethanol/water ice block and then starts to penetrate into the pores and cracks of the ethanol/water ice block. In the final stage, nearly all the Xe polarization is in the gas phase above the liquid and trapped inside the pores. NMR spectra of homogeneous samples of pure ethanol containing thermally polarized Xe and the spectroscopic images of the melting process show that very high concentrations of hyperpolarized Xe (about half of the density of liquid Xe) can be stored or delivered in pure ethanol.
我们利用核磁共振（NMR）光谱法、成像技术以及通过超极化129Xe进行的时间分辨光谱成像方法，可视化了氙（Xe）冰在不同溶剂中的熔化和溶解过程。从超极化固态Xe层冻结在乙醇（乙醇/水）冰块顶部的初始状态开始，我们测量了Xe的相变随时间和温度的变化。在纯乙醇样品中，Xe冰块首先穿过粘性乙醇落到样品管底部，然后形成一层薄的液态Xe/乙醇层。氙原子被困在该液态层中直至室温，并在11分钟的时间段内保持其磁化强度。在乙醇/水混合物（80体积%/20%）中，大部分极化的Xe液体首先停留在乙醇/水冰块顶部，然后开始渗透到乙醇/水冰块的孔隙和裂缝中。在最后阶段，几乎所有的Xe极化都处于液体上方的气相中并被困在孔隙内。含有热极化Xe的纯乙醇均匀样品的NMR光谱以及熔化过程的光谱图像表明，非常高浓度的超极化Xe（约为液态Xe密度的一半）可以在纯乙醇中储存或传输。
