Formation, Dynamics, and Applications of Ultracold Molecules

超冷分子的形成、动力学和应用

• 批准号: 1208317
• 负责人: William Stwalley
• 金额: $ 46万
• 依托单位: University of Connecticut
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2012
• 资助国家: 美国
• 起止时间: 2012-09-01 至 2016-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1208317&HistoricalAwards=false
• 关键词: Formation; Dynamics; Applications; Ultracold; Molecules

This grant enables the PIs to continue and expand their research program on the formation, dynamics, and applications of ultracold molecules at sub-miliKelvin temperatues. Prior research by the group has focused on diatomic alkali molecules produced by the process of ultracold photoassociation, in which pairs of ultracold alkali metal atoms are associated into bound vibrational levels of electronically excited molecular states. These electronically excited molecules then decay by spontaneous emission of light, some to near-dissociation rovibrational levels of the singlet ground state (the X state) or the metastable triplet state (the a state). New experiments will focus on methods to efficiently create KRb and Rb2 molecules in the lowest rovibrational levels of both the stable X state, X(v=0, J=0), and the metastable a(0,0) state. The program also includes related studies of radiative lifetimes and collisions.Two promising methods for continuous and simple production of X(0,0) are: (1) resonance-enhanced coupling of two different electronic states, one with long-range character to enhance photoassociation and the other with short-range character to enhance decay to X(0,0); (2) Feshbach-Optimized Photoassociation (FOPA) in a magnetic field to greatly enhance photoassociation rates by mixing of high levels of the X and a states, again to enhance the short-range character of the wave function. For the metastable a(0,0) state, a novel "blue-detuned" photoassociation scheme can produce large populations, and is being used to study the purely radiative lifetime at low density as well as inelastic and reactive collisions in an optical trap.By trapping ultracold molecules at high densities, the group seeks to observe for the first time ultracold atom-molecule photoassociation. This will produce ultracold triatomic molecules such as Rb3 and KRb2 in previously unexplored excited states, which can be detected either by laser ionization or autoionization.Interest in X(0,0) molecules is particularly strong because only in this quantum state can it be assured that collisions will not cause heating due to changes in the internal quantum state. This enables long trapping times and investigations of subtle quantum interactions. Possible applications of cold polar molecules for quantum information are of great current interest, and at high enough densities even a molecular Bose-Einstein condensate becomes a possibility. The new production methods explored in this project offer large advantages in simplicity over alternative approaches such as Raman transfer in quantum degenerate gases, and they enable continuous or near-continuous generation of cold molecules. Systematic studies of the spectroscopy and dynamics of these cold molecules will provide much-needed data and physical insights to inform future investigations of both ultracold and room-temperature molecules.The project will be well-integrated into the large ultracold physics program at the University of Connecticut, currently including seven faculty and about 40 students and postdoctoral fellows. Elements of this integration include project-based group meetings, mentoring, workshops, seminars, and numerous national and international collaborations. Presentations by our research group members locally and at meetings and other educational institutions contribute to scientific understanding. Broader long term benefits include new understanding and applications in areas such as ultracold chemistry, measurements of fundamental symmetries and physical constants, quantum information science, and nanoscience, as well as improved international collaboration.

这笔资助使 PI 能够继续并扩大他们关于亚开尔文温度下超冷分子的形成、动力学和应用的研究项目。该小组之前的研究重点是超冷光缔合过程产生的双原子碱分子，其中成对的超冷碱金属原子缔合成电子激发分子态的束缚振动能级。然后，这些电子激发的分子通过自发发射光而衰变，其中一些衰变至单重基态（X 态）或亚稳态三重态（a 态）的近解离振动能级。新实验将重点关注在稳定 X 态 X(v=0, J=0) 和亚稳态 a(0,0) 态的最低振动水平下有效创建 KRb 和 Rb2 分子的方法。该计划还包括辐射寿命和碰撞的相关研究。连续且简单地产生X(0,0)的两种有前途的方法是：(1)两种不同电子态的共振增强耦合，一种具有长程特征以增强光缔合，另一种具有短程特征以增强X(0,0)的衰变； (2) 磁场中的 Feshbach 优化光缔合 (FOPA)，通过混合高水平的 X 和 a 态大大提高光缔合速率，再次增强波函数的短程特性。对于亚稳态a(0,0)态，一种新颖的“蓝色失谐”光缔合方案可以产生大量群体，并被用于研究低密度下的纯辐射寿命以及光陷阱中的非弹性和反应性碰撞。通过在高密度下捕获超冷分子，该小组试图首次观察超冷原子-分子光缔合。这将产生以前未探索过的激发态的超冷三原子分子，例如Rb3和KRb2，可以通过激光电离或自电离来检测。人们对X(0,0)分子的兴趣特别强烈，因为只有在这种量子态下才能保证碰撞不会因内部量子态的变化而导致加热。这使得较长的捕获时间和对微妙量子相互作用的研究成为可能。目前，冷极性分子在量子信息方面的可能应用引起了人们的极大兴趣，并且在足够高的密度下，甚至分子玻色-爱因斯坦凝聚体也成为可能。该项目探索的新生产方法与量子简并气体中的拉曼传输等替代方法相比，在简单性方面具有巨大优势，并且能够连续或近乎连续地生成冷分子。对这些冷分子的光谱和动力学的系统研究将提供急需的数据和物理见解，为未来对超冷和室温分子的研究提供信息。该项目将很好地融入康涅狄格大学的大型超冷物理项目，该项目目前包括 7 名教员和约 40 名学生和博士后。这种整合的要素包括基于项目的小组会议、指导、讲习班、研讨会以及众多的国内和国际合作。我们的研究小组成员在当地以及在会议和其他教育机构上的演讲有助于促进科学理解。更广泛的长期利益包括在超冷化学、基本对称性和物理常数的测量、量子信息科学和纳米科学等领域的新理解和应用，以及改善的国际合作。