Quantum Phenomena in Systems Containing Matrix Isolated Atomic Free Radicals

非技术摘要当混合的氮或氢原子和分子的射流被收集在超流氦烧杯中时，就形成了一个由被非常薄的固体氦层包围的原子和分子的小簇组成的凝胶状网络。这种多孔物质被称为杂质氦固体。这些团簇包含大量的这些原子(自由基)，这些原子被团簇中包含的周围分子以及固体氦层稳定下来，防止重新组合成分子。研究人员将研究储存在捕获的自由基中的化学能量，当它们重新结合成分子时，这些能量可以释放出来。调查将主要使用磁共振和光学光谱学。将研究量子力学驱动的化学反应，这种反应即使在绝对零度也可以发生，并可以导致自由氢原子和束缚在分子中的氢原子之间的交换。在最低温度下，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，可能会导致超流。在这个项目中培训的博士后和学生将获得低温和磁共振方面的研究技能，这些技术在许多科学和技术领域都有广泛的实用价值。*技术摘要*本研究计划将涉及分别嵌入氢或氮分子的分子矩阵中的氢或氮原子的研究。基质可以是块状分子固体，也可以是由分子固体的纳米簇组成的多孔凝胶(杂质-氦固体)，每个分子固体的周围都有一层或两层固体氦。由此产生的原子自由基的基质隔离稳定了它们，使它们不会重新组合成分子，从而允许对它们进行多天的研究。这些体系的性质将在从4K到100MK或更低的温度范围内进行研究。将使用磁共振、低频磁化率和光学光谱学。将进行磁性有序、隧道交换化学反应和磁弛豫的研究。我们将在嵌入的氢原子中寻找可能的玻色-爱因斯坦凝聚。该项目的学生和博士后将在低温和磁共振方面接受良好的培训，这两项技术都是科学和技术中的重要技术。基质分离领域有许多可能的变化和未知之处有待探索，这让年轻人接触到了发现的兴奋。

******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.