Studies with Liquid Helium Films

小行星9729805 这一建议将支持实验低温的一个组成部分， 物理 程序 在 的 大学 来自马萨诸塞州/阿默斯特。 目标是：（1）研究He-3-He-4混合物膜系统的新方面，（2）更详细地研究多孔材料中氦的毛细冷凝和雪崩现象，（3）在一维和二维中对图案化衬底上的氦膜进行研究，重点是二维局部化，（4）总结了我们在C_（60）衬底上对氦的研究。 实验方法包括石英晶体共振、第三声和He- 3/He-4热性质的热容研究 混合物 电影; 和 高 决议 多孔材料中毛细凝聚和雪崩事件的电容测量。这项工作将导致对氦对氢的更好的理解，包括混合物情况下的“两个转变” 电影;适当性的测试 的 最近的理论工作有关雪崩事件的磁性系统， 在滞后毛细冷凝中看到的类似事件的描述，以及对用于确定多孔材料中的孔隙分布和排水现象的方法的更好理解。 除了有助于理解氦膜本身行为的进展外，这项工作还将与费米系统、雪崩现象、毛细凝聚和非线性现象等领域的更广泛社区相关。 该项目为研究生提供了一些重要技术的优秀培训， 在技术领域以及基础研究项目。 %氦是一种非常重要的物质，当冷却到接近绝对零度时，它具有特殊的液体性质。这项拟议的拨款将用于研究凝聚态物质物理学中的各种问题，利用液氦的独特性质，特别是液氦薄膜，作为促进研究的工具。 在某些情况下，氦本身将成为研究的主题，在其他情况下，氦将作为一种方便的流体来探索感兴趣的现象。特别是，赠款将允许研究He-4和He-3/He-4混合物薄膜，从而提高 我们对二维表面和弱结合基质（如氢）上相变的理解。 将研究多孔材料中的毛细冷凝现象和雪崩事件，以更深入地了解多孔材料如何排水，这是使用普通液体无法达到的理解。最后，总结了氦在C60衬底上的研究。该项目为研究生提供了一些重要技术的优秀培训， 在技术领域以及基础研究项目。 ***

9729805 Hallock This proposal will support a component of the experimental low temperature physics program at the University of Massachusetts/Amherst. The objectives are: (1) to study new aspects of the He-3-He-4 mixture film system, (2) to study in more detail capillary condensation and avalanche phenomena with helium in porous materials, (3) to conduct studies with helium films on patterned substrates in one and two dimensions, with a focus on two dimensional localization, and (4) to bring to a conclusion our study of helium in the context of C60 substrates. Experimental methods include quartz crystal resonance, third sound, and heat capacity studies of the thermal properties of He- 3/He-4 mixture films; and high resolution capacitance measurements of capillary condensation and avalanche events in porous materials. The work will lead to an improved understanding of helium on hydrogen, including "two transitions" in the case of mixture films; a test of the appropriateness of recent theoretical work concerning avalanche events in magnetic systems for the description of similar events seen in hysteretic capillary condensation, and an improved understanding of a method for determining pore distributions and draining phenomena in porous materials. In addition to contributing to progress in understanding the behavior of helium films themselves, the work will have relevance to the wider community in the areas of Fermi systems, avalanche phenomena, capillary condensation, and non- linear phenomena. The project provides excellent training for graduate students in a number of important techniques that are used in technical fields as well as fundamental research projects. %%% Helium is a remarkable substance with special liquid properties when cooled near the absolute zero of temperature. This proposed grant will study various problems in condensed m atter physics using the unique properties of liquid helium, particularly liquid helium films, as the vehicle to facilitate the study. In some cases the helium itself will be the subject of the study, in others, helium will serve as a convenient fluid to explore the phenomena of interest. In particular, the grant will allow study He-4 and He-3/He-4 mixture films and thereby enhance our understanding of phase transitions on two dimensional surfaces and on weak binding substrates such as hydrogen. Capillary condensation phenomena and avalanche events in porous materials will be studied to gain a deeper understanding of how porous materials drain, an understanding that cannot be reached using ordinary liquids. Finally, studies of helium on C60 substrates will be concluded. The project provides excellent training for graduate students in a number of important techniques that are used in technical fields as well as fundamental research projects. ***