Beam Deflection Studies of Cold Molecules and Complexes Entrapped in Helium Nanodroplets: Permanent, Metastable, and Laser-Induced Electric and Magnetic Dipole Moments

在这个项目中，南加州大学的Vitaly Kresin教授小组将研究由纳米级超流氦液滴束携带的极冷分子中的电荷和磁流的分布，该项目得到化学学部化学结构、动力学和机制（CSDM-A）项目的支持。这些分布揭示了分子结构、运动和成键的信息。纳米液滴将通过外部施加的电场或磁场，并测量其轨迹的场致偏转。这项研究将包括生物分子的电和磁结构、原子和分子复合物、“分子磁体”以及其他无法通过其他方法精确测量甚至合成的系统。该项目还将演示通过外部电场控制分子反应，并通过可调谐激光检测分子电极性的切换。该项目将产生与基础研究和应用广泛相关的新知识，从蛋白质形成到超冷化学，从自旋电子学到有机合成，从大气化学到量子信息科学。研究生和本科生将在一个高度跨学科的研究领域进行指导，并参与科学展览和学校外展计划。该项目将与一门组合化学本科实验课程建立合作关系。纳米液滴是通过氦气的超音速膨胀形成的，它会将分子、原子或蒸汽团嵌入到吸收电池中，然后穿过一个强而不均匀的电场或磁场。该场将定向超冷极性杂质并施加强烈的偏转力，导致光束的可测量偏差，从而能够直接读出分子或复合物的电或磁偶极矩。该技术将应用于过氧化氢簇、氨基酸二聚体和二肽、高自旋碱二聚体和分子磁体。此外，该项目将展示预定向分子的组装，以及基于偏转的光致变色分子的作用光谱。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

In this project, supported by the Chemical Structure, Dynamics, and Mechanisms (CSDM-A) Program of the Division of Chemistry, Prof. Vitaly Kresin’s group at the University of Southern California will study the distributions of electrical charges and magnetic currents within extremely cold molecules carried by a beam of nanoscale droplets of superfluid helium. These distributions reveal information about molecular structure, motion, and bonding. The nanodroplets will pass through an externally applied electric or magnetic field, and the field-induced deflection of their trajectories will be measured. The study will encompass the electric and magnetic structure of biological molecules, atomic and molecular complexes, “molecular magnets,” and other systems that are impractical to accurately measure, or even synthesize, by other means. The project also will demonstrate steering of a molecular reaction by an external electric field and detecting the switching of the electric polarity of a molecule by a tunable laser. The project will lead to new knowledge that has broad relevance to basic research and applications ranging from protein formation to ultracold chemistry, spintronics to organic synthesis, and atmospheric chemistry to quantum information science. Graduate and undergraduate students will be mentored in a highly interdisciplinary research field and engage in science fairs and school outreach programs. A collaboration between the project and an undergraduate laboratory course in combinatorial chemistry will be established.The nanodroplets, formed via supersonic expansion of helium gas, will embed molecules, atoms, or clusters from vapor in pick-up cells, and then traverse a strong inhomogeneous electric or magnetic field. This field will orient the ultracold polar impurities and exert an intense deflecting force, resulting in a measurable deviation of the beam, thus enabling direct readout of the electric or magnetic dipole moment of the molecule or complex. This technique will be applied to hydrogen peroxide clusters, amino acid dimers and dipeptides, high-spin alkali dimers, and molecular magnets. Furthermore, the project will demonstrate the assembly of pre-oriented molecules, and deflection-based action spectroscopy of photochromic molecules.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.