Quantum Phenomena in Systems Containing Matrix Isolated Atomic Free Radicals

* 非技术摘要 ** 当氮或氢原子和分子的混合射流被收集在一个装有超流氦的烧杯中时，就会形成一个由原子和分子的小簇组成的凝胶状网络，周围环绕着非常薄的固体氦层。 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），这些原子被团簇中所含的周围分子以及固体氦层稳定下来，不会重组成分子。 将对储存在被捕获的自由基中的化学能进行研究，这些自由基在重新组合成分子时可以释放出来。 调查将主要采用磁共振和光谱学。将研究量子力学驱动的化学反应，这种反应甚至可以在绝对零度下发生，并可以导致自由氢原子和分子中结合的氢原子之间的交换。 在极低的温度下，原子氢自由基甚至可能经历玻色-爱因斯坦凝聚，这是一种极端形式的量子行为，可以引起超流性。 博士后和学生在这个程序中接受培训将获得低温和磁共振，在科学和技术的许多领域具有广泛的实用性技术的研究技能。 * 技术摘要 ** 本研究计划将涉及分别嵌入由氢或氮分子组成的分子基质中的氢或氮原子的研究。 基质可以是大块分子固体或由分子固体的纳米团簇组成的多孔凝胶（杂质-氦固体），每个分子固体被单层或两个固体氦包围。 由此产生的原子自由基的基质隔离使它们稳定下来，防止它们重组成分子，使它们能够被研究许多天。 这些系统的性质将在从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。 该计划的学生和博士后将在低温和磁共振方面得到良好的培训，这两项技术都是科学和技术的重要技术。 矩阵隔离领域有许多可能的变化和未知的探索，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.