Dynamics of Molecules in Extreme Rotational States Made with an Optical Centrifuge

在化学系化学结构、动力学和机理a （CSDM-A）项目的支持下，马里兰大学帕克分校的Amy Mullin教授和她的团队将研究分子在具有显著旋转能量时的行为。当能量增加时，通常以温度升高的形式增加，许多化学反应进行得更快。增加热量可以使分子形成高能结构，从而转化为其他分子。在宏观世界中，能量是一种平滑变化的性质。然而，分子在绝对意义上是小的，它们的能级是由量子力学决定的。一个二氧化碳分子的长度是500亿分之一厘米，当它旋转时，当它的原子内部振动时，它具有离散的能级。这些量子化的能量状态控制着在高能条件下帮助或阻碍化学变化的分子运动类型。该项目的重要性在于确定分子几何结构是如何被大量旋转能量扭曲的，以及这种扭曲是如何导致新型化学过程的。这个项目的结果将对理解化学反应产生影响，并有望为高能分子存在的其他领域的研究提供信息。研究生将有机会获得基于复杂激光方法的经验。为化学和生物化学本科学生准备研究生入学培训。根据该合同，马里兰大学的Mullin小组将使用超快、可调光学离心机制备具有定向角动量的极端旋转能态分子。利用高分辨率瞬态红外光谱研究高能分子的结构和动力学。光学离心机是一种强场、非共振技术，可以诱导分子中角动量的大幅增加，从而进入一个以前未探索的领域。该项目将准备具有可控能量的新生旋转分布，并研究分子如何经历碰撞松弛，取向各向异性衰变以及耦合到振动模式。该项目将研究能量间隙、角频率和旋转量子数如何影响动力学。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。

With support from the Chemical Structure, Dynamics and Mechanisms-A (CSDM-A) Program in the Division of Chemistry, Professor Amy Mullin and her team at the University of Maryland-College Park will investigate how molecules behave when they possess significant rotational energy. Many chemical reactions proceed faster when energy is added, usually in the form of increased temperature. Adding heat allows molecules to adopt high-energy configurations from which they can convert into other molecules. In the macroscopic world, energy is a smoothly varying property. However, molecules are small in an absolute sense, and their energy levels are determined by quantum mechanics. A CO2 molecule is 50 billionths of a centimeter in length, and it has discrete energy levels when it rotates and when its atoms vibrate internally. These quantized energy states control the types of molecular motion that help, or hinder, chemical change under high-energy conditions. The importance of the project is to determine how molecular geometry is distorted by large amounts of rotational energy and how this distortion leads to new types of chemical processes. The results of this project will have implications for understanding chemical reactions and are expected to inform research in other fields where high energy molecules are present. Graduate students will have the opportunity to gain experience in sophisticated laser-based approaches. Training workshops will be organized to prepare undergraduate chemistry and biochemistry students for applying to graduate school. Under this award, the Mullin group at U. Maryland will use an ultrafast, tunable optical centrifuge to prepare molecules in extreme rotational energy states with oriented angular momentum. The structure and dynamics of the high energy molecules will be interrogated using high-resolution transient infrared spectroscopy. The optical centrifuge is a strong-field, non-resonant technique that can induce large angular momentum increases in molecules, thereby giving access to a previously unexplored realm. The project will prepare nascent rotational distributions with controllable amounts of energy, and investigate how the molecules undergo collisional relaxation, orientational anisotropy decay, and coupling to vibrational modes. The project will investigate how energy gaps, angular frequencies, and rotational quantum numbers impact the 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.