Accurate Methods for Ultracold Reactions with Product Quantum State Resolution

超冷分子为高分辨率分子光谱学，量子信息处理和分子事件的受控询问提供了前所未有的机会，包括最终量子体系中的化学反应性。 它们的碰撞和相互作用的定量描述需要量子力学方法，但对于当前冷却和捕获实验感兴趣的许多分子来说，这在计算上具有挑战性。主要的困难是扩散的量子态和自由度的数量要包括在计算和结果的敏感性，以短程和长程分子间的力量。这项工作将开发新的理论和计算工具，超越现有的模型，用于处理温度低于1开尔文的化学反应。它将大大提高在低温和超低温下描述化学反应的理论能力，并为低温下化学反应的量化研究提供有效的工具。拟议的研究超越了学科界限，开发的计算算法也将同样适用于从大气化学到天体物理学等不同环境中的分子过程。 该项目的资助也将有助于未来科学和技术领域的劳动力发展。该项目涉及开发准确和有效的方法来研究冷分子碰撞中的化学反应和能量转移。将继续开发和优化完整的紧密耦合（CC）方法。还将开发和基准测试一种在短距离使用全CC和在长距离使用多通道量子亏损理论（MQDT）的混合方法。这些方法将被应用于包括F + H 2和OH + H在内的许多反应。此外，PI将探索几何相在化学反应动力学中的重要性，使用超冷极限下的O + OH反应作为说明性案例。

Ultracold molecules offer unprecedented opportunities for high-resolution molecular spectroscopy, quantum information processing, and controlled interrogation of molecular events, including chemical reactivity in the ultimate quantum regime. A quantitative description of their collisions and interactions requires a quantum mechanical approach, but it is computationally challenging for many molecules of interest to current cooling and trapping experiments. The primary difficulty is the proliferation in the number of quantum states and degrees of freedom to be included in the calculations and the sensitivity of results to both short-range and long-range intermolecular forces. This work will develop new theoretical and computational tools that go beyond existing models for the treatment of chemical reactions at temperatures below 1 degree Kelvin. It will significantly enhance theoretical capabilities for the description of chemical reactions at cold and ultracold temperatures and provide an efficient tool for quantized studies of chemical reactions at low temperatures. The proposed research transcends disciplinary boundaries, and the computational algorithms developed will also be equally applicable to molecular processes in diverse environments ranging from atmospheric chemistry to astrophysics. Funding of this project will also contribute to future workforce development in Science and Technology.This project deals with the development of accurate and efficient methods to study chemical reactions and energy transfer in cold molecular collisions. The full Close-Coupling (CC) method will continue to be developed and optimized. A hybrid method that uses full CC at short range and Multi-Channel Quantum Defect Theory (MQDT) at long range will also be developed and benchmarked. These methods will be applied to a number of reactions including F + H2 and OH + H. In addition, the PI will explore the importance of the geometric phase in chemical reaction dynamics using the O + OH reaction at the ultracold limit as a illustrative case.