Linear and Nonlinear Spin Transport in Random Porous Media

9501171将利用核磁共振（NMR）和其他技术来研究扩散和色散粒子和波在三种类型系统中的传播。第一种是随机多孔介质中的自旋极化量子流体。 例如，将纯~ 3 He液体和微珠包和二氧化硅气凝胶孔隙中的~ 3 He-~ 4 He混合物用8 - 10 T磁锉极化并冷却到10 mK以下，以研究混合物相图、量子局域化效应和干涉 和自旋波的局部化。第二个系统是室温下多孔介质中的流体。脉冲场梯度核磁共振将被用来研究孔隙空间的几何结构，并研究在一个广泛的Peclet数的应用流中的痕量分散。 最后，非线性波将在极化量子流体和室温水波实验中进行研究，以测试逆谱变换对物理系统的适用性。 该项目的目标是更好地了解粒子和波在具有随机结构的复杂物理系统中的传播。核磁共振（NMR）将用于研究填充细粉、硅胶和天然岩石等材料孔隙的流体中分子的运动。 这些研究将在量子效应占主导地位的极低温度和室温下进行， 发现经典行为的地方。 的 低温 研究将检验理论 相关 到 电子在金属和半导体中的传播。 室温工作将发展研究多孔材料结构的新方法，并将检验有关示踪剂通过流体流动分散的理论。非线性波也将 被 在一个子项目中研究，该项目旨在吸引本科生参与研究。

9501171 Candela Nuclear magnetic resonance (NMR) and other techniques will be used to study the propagation of diffusing and dispersing particle and waves in three types of system. The first consists of spin-polarized quantum fluids in random porous media. For example, pure 3He liquid and 3He-4He mixtures in the pores of bead packs and silica aerogel will be polarized by an 8 - 10 T magnetic files and cooled below 10 mK to study the mixture phase diagram, quantum localization effect, and interference and localization of spin waves. The second system is fluids in porous media at room temperature. Pulsed-field-gradient NMR will be used to study the geometric structure of the pore space, and to study trace dispersion in an applied flow over a wide range of Peclet numbers. Finally, nonlinear waves will be studied both in polarized quantum fluids and in a room-temperature water-wave experiment to test the applicability of the inverse spectral transform to physical systems. %%% The objective of this project is to better understand the propagation of particles and waves in complex physical systems that have a random structure. Nuclear magnetic resonance (NMR) will be used to study the motions of molecules in fluids filling the pores of materials like fine powders, silica gels, and natural rock. The studies will take place both at very low temperature, where quantum effects will dominate, and at room temperature, where classical behavior is found. The low temperature studies will test theories relevant to the propagation of electrons in metals and semiconductors. The room temperature work will develop new methods for studying the structure of porous materials, and will test theories concerning the dispersion of tracers by fluid flow. Nonlinear waves will also be studied in a sub-project geared toward engaging undergraduate students in resear ch. ***