Quantum Control of Molecules Using Dressed States Created by Laser Radiation

该项目将有助于利用激光控制分子量子态的机制的发展。一般来说，分子不是球对称的物体，因此大多数涉及分子的碰撞过程强烈地依赖于碰撞伙伴的相对排列。了解原子和分子之间碰撞过程的基本物理学对于许多研究领域都很重要，包括化学反应性、涉及超冷原子和分子的过程动力学以及星际介质的天体物理学。分子也有一个复杂的内部结构，由于无数的方式，化学键可以实现。这导致了丰富多样的内部量子态，这些量子态经常相互作用。这种相互作用可以引起共价和离子之间化学键性质的变化，也可以在预解离过程中由于吸引电子态和排斥电子态之间的耦合而导致化学键的断裂。在电磁场（光）的存在下，原子或分子的能级被电磁辐射改变（“修饰”）。本项目的目标之一是利用这一现象，通过有选择地探测分子在碰撞过程中旋转角动量的排列变化，来研究分子碰撞过程的动力学。量子态选择性将通过利用控制激光的奥特勒-汤斯（AT）效应去除分子目标旋转态的磁亚能级的简并来实现。此外，通过耦合激光修饰分子状态将用于测量电子跃迁偶极矩，并演示在锂二聚体共价电位和离子电位之间避免交叉区域的预解离控制。此外，修饰态方法使得利用自旋轨道相互作用作为分子价电子自旋极化的工具成为可能。自旋轨道相互作用是由于电子的内部磁矩（自旋）与电子轨道运动引起的磁场之间的耦合而产生的。在这种情况下，奥特勒-汤斯效应将使分子在单线态（反平行自旋）和三重态（平行自旋）之间切换成为可能。实现这种“自旋开关”在量子计算中有潜在的应用。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。

This project will contribute to the development of control mechanisms of molecular quantum states using laser light. In general, molecules are not spherically symmetric objects, and as a result most collisional processes involving them depend strongly on the relative alignment of the colliding partners. Understanding the basic physics of collisional processes between atoms and molecules is of importance for a number of research areas including chemical reactivity, the dynamics of processes involving ultracold atoms and molecules, and astrophysics of the interstellar medium. Molecules also have an elaborate internal structure due to the innumerable ways in which chemical bonds can be realized. This leads to a rich variety of internal quantum states that often interact with each other. Such interactions can cause changes in the nature of the chemical bond between covalent and ionic and also give can rise to breaking of the chemical bond due to couplings between attractive and repulsive electronic states in the process of predissociation. In the presence of an electromagnetic field (light), the energy levels of an atom or a molecule are modified ("dressed") by the electromagnetic radiation. One of the goals of this project is to use this phenomenon to study the dynamics of molecular collisional processes by probing selectively the change in the alignment of the molecular rotational angular momentum during collisional processes. Quantum state selectivity will be achieved by removing the degeneracy of the magnetic sublevels of the target rotational state of the molecules using the Autler-Townes (AT) effect of a control laser. In addition, dressing of molecular states by a coupling laser will be used to measure the electronic transition dipole moments and to demonstrate control of predissociation in regions of avoided crossings between covalent and ionic potentials of the lithium dimer. Furthermore, the dressed states approach makes it possible to use the spin-orbit interaction as a tool for molecular valence electron spin polarization. The spin-orbit interaction arises due to the coupling between the internal magnetic moment (spin) of the electrons and the magnetic field caused by the orbital motion of the electrons. The Autler-Townes effect, in this context, will make it possible to switch the molecules between a singlet (antiparallel spins) state and a triplet (parallel spins) state. Realizing this "spin switch" has potential applications in quantum computing.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.