Molecular Rydberg Spectra Encode Intramolecular Dynamics

分子通常包含许多电子，并且由于带负电荷，这些电子在空间中移动时会相互排斥。电子-电子斥力使得精确计算分子的性质和行为变得困难，这仍然是化学科学面临的最大挑战之一。在化学系化学结构、动力学和机理a项目的支持下，麻省理工学院的Robert Field教授和他的研究小组正在使用先进的激光和微波光谱技术来制备和研究所谓的里德伯分子。里德伯分子是一种正常的分子，其中一个电子（通过激光）被激发到如此高的轨道，以至于该系统类似于一个简单的氢原子（一个带负电的电子加上一个带正电的质子）。由于它们的简单性，里德伯分子可以用理论更精确地建模，并且可以更准确地回答其他问题，例如，电子如何与光相互作用？或者电子如何相互交换能量，以及如何与分子中带正电的“离子核”交换能量？这个研究项目挑战了关于分子结构以及它们如何与光相互作用的传统思维。这个项目的发现也可能对量子计算的新领域产生影响。参与该项目的博士后科学家和本科生研究人员正在积累前沿激光/微波技术和计算化学的经验。这个项目主要有三个实验目标，并针对三个基本问题的答案。对主要实验成分的可行性进行了独立论证。实验目标是：(i)以每秒100,000分辨率元素的光谱速度记录Rydberg-Rydberg光谱，由一套实时诊断系统组织和分配；（ii）利用系统的光谱途径进入核非穿透里德堡态，绕过以前认为不可能的快速非辐射衰变区域（称为“死亡区”）；（iii）利用Rydberg-Rydberg跃迁的超辐射来获得量子多体相互作用的信息。如果这些实验成功，我们的方法和结果将挑战光谱学家想象和瞄准气相分子光谱的新领域。该项目为确定分子离子的多极矩和极化率提供了新的方法，这是建立致密等离子体模型所必需的，与天体物理学和新技术相关。多通道量子缺陷理论的改进为状态选择分子离子的产生提供了先验的校准方法，并为分子动力学的外部控制设计了新的方案。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。

Molecules typically contain many electrons, and, being negatively charged, these electrons repel each other as they move in space. Electron-electron repulsion makes it difficult to calculate precisely the properties and behaviors of molecules, and remains one of the greatest challenges for the science of chemistry. With the support of the Chemical Structure, Dynamics and Mechanisms-A Program of the Division of Chemistry, Professor Robert Field and his research team at the Massachusetts Institute of Technology are using advanced laser and microwave spectroscopy techniques to prepare and interrogate what are called Rydberg molecules. A Rydberg molecule is a normal molecule in which one electron has been excited (by laser light) to such a high orbit that the system resembles a simple hydrogen atom (one negatively charged electron plus one positively charged proton). Because of their simplicity, Rydberg molecules can be modeled more accurately with theory, and it becomes possible to answer other questions with more accuracy, for example, how do electrons interact with light? Or how do electrons exchange energy with each other and with the positive-charged "ion core" of the molecule? This research project challenges conventional thinking about the structure of molecules and how they interact with light. The discoveries from this project may also have implications for the new field of quantum computing. The post-doctoral scientists and undergraduate researchers engaged in this project are gaining experience in both cutting-edge laser/microwave technology and computational chemistry. This project is focused on three experimental goals and targeted at answers to three fundamental questions. The feasibilities of the principal experimental components have been independently demonstrated. The experimental goals are: (i) to record Rydberg-Rydberg spectra at a spectral velocity of 100,000 resolution elements per second, organized and assigned by a suite of on-the-fly diagnostics; (ii) to exploit systematic spectroscopic access to core-nonpenetrating Rydberg states, bypassing a region of fast nonradiative decay previously deemed to be impassible (called the "zone of death"); (iii) to exploit superradiance on Rydberg-Rydberg transitions to obtain information about quantum many-body interactions. If these experiments are successful, our methods and results will challenge spectroscopists to imagine and target new frontiers for the spectroscopy of gas phase molecules. This project is leading to new methods for the determination of multipole moments an polarizabilities of molecular-ions, which are essential to model dense plasmas, which are relevant to astrophysics and new technologies. The refinement of Multi-channel Quantum Defect Theory promises a priori calibrated methods for production of state-selected molecular ions devise new classes of schemes for external control of molecular dynamics.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.