Quantum Phenomena in Systems Containing Matrix Isolated Atomic Free Radicals

******非技术摘要******当一束混合的氮或氢原子和分子被收集到一个充满超流氦的烧杯中时，一个由原子和分子的小簇组成的凝胶状网络被非常薄的固体氦层包围。这种多孔物质被称为杂质氦固体。团簇中含有大量的这些原子（自由基），这些原子被团簇周围的分子以及固体氦层所稳定，不会重新组合成分子。研究人员将研究储存在被困自由基中的化学能，当自由基重组成分子时，这些化学能就会释放出来。研究将主要使用磁共振和光谱学。量子力学驱动的化学反应，即使在绝对零度也能发生，并能导致自由氢原子和结合在分子中的氢原子之间的交换，将被研究。在极低的温度下，原子氢自由基甚至可能发生玻色-爱因斯坦凝聚，这是量子行为的一种极端形式，可以产生超流动性。该项目培养的博士后和学生将获得低温和磁共振等在许多科学技术领域有广泛应用的研究技能。******技术摘要******本研究计划将涉及分别嵌入氢或氮分子组成的分子基质中的氢或氮原子的研究。基质既可以是大块的分子固体，也可以是由分子固体的纳米团簇组成的多孔凝胶（杂质-氦固体），每个分子固体都被一层或两层固体氦包围。由此产生的原子自由基的基质分离稳定了它们，防止它们重新组合成分子，使它们能够被研究许多天。这些系统的性质将在4 K到100 mK或更低的温度范围内进行研究。将采用磁共振、低频磁化率和光谱学。将进行磁有序、隧道交换、化学反应和磁弛豫的研究。将在嵌入的氢原子中寻找可能的玻色-爱因斯坦凝聚。本项目的学生和博士后将在低温学和磁共振这两项重要的科学技术方面受到良好的训练。矩阵分离领域有许多可能的变化和未知有待探索，让年轻人接触到发现的兴奋。

******NON-TECHNICAL ABSTRACT******When a jet of mixed nitrogen or hydrogen atoms and molecules is collected in a beaker of superfluid helium, a gel-like network consisting of small clusters of the atoms and molecules surrounded by very thin layers of solid helium is formed. This porous substance is known as an impurity-helium solid. The clusters contain large concentrations of these atoms (free radicals), which are stabilized against recombination into molecules by the surrounding molecules contained in the clusters as well as the layers of solid helium. Studies will be made of the chemical energy stored in the trapped free radicals, which can be released when they recombine into molecules. Investigations will primarily employ magnetic resonance and optical spectroscopy. Quantum mechanically driven chemical reactions, which can occur even at absolute zero and can lead to exchange between free hydrogen atoms and hydrogen atoms bound in molecules, will be studied. At the very lowest temperatures, the atomic hydrogen free radicals may even undergo Bose-Einstein condensation, an extreme form of quantum behavior that can give rise to superfluidity. Postdocs and students trained in this program will acquire research skills in cryogenics and magnetic resonance, techniques that have wide utility in many areas of science and technology. ******TECHNICAL ABSTRACT******This research program will involve studies of hydrogen or nitrogen atoms embedded in molecular matrices consisting of hydrogen or nitrogen molecules, respectively. The matrices can be either bulk molecular solids or porous gels (impurity-helium solids) composed of nanoclusters of the molecular solids, each of which is surrounded by a monolayer or two of solid helium. The resulting matrix isolation of the atomic free radicals stabilizes them against recombination into molecules, allowing them to be studied for many days. Properties of these systems will be investigated at temperatures ranging from 4 K down to 100 mK or less. Magnetic resonance, low frequency magnetic susceptibility and optical spectroscopy will be employed. Studies of magnetic ordering, tunneling exchange chemical reactions, and magnetic relaxation will be performed. A search will be made for possible Bose-Einstein condensation in the embedded hydrogen atoms. The students and postdocs in this program will be well trained in cryogenics and magnetic resonance, both important techniques in science and technology. The field of matrix isolation has many possible variations and unknowns to be explored, giving young people exposure to the excitement of discovery.