Formation, Dynamics, and Applications of Ultracold Molecules

这笔赠款使PI能够继续并扩大他们在亚开尔文温度下的超冷分子的形成、动力学和应用的研究计划。该小组之前的研究重点是通过超冷光缔合过程产生的双原子碱分子，在这个过程中，成对的超冷碱金属原子被缔合成电子激发的分子态的束缚振动能级。然后，这些被电子激发的分子通过自发发光而衰变，其中一些分子达到单重态(X态)或亚稳态三重态(a态)的近解离振动能级。新的实验将集中于在稳定的X态X(v=0，J=0)和亚稳态a(0，0)的最低振动能级中有效地产生Krb和Rb2分子的方法。该程序还包括对辐射寿命和碰撞的相关研究。两种有希望的简单连续产生X(0，0)的方法是：(1)两种不同电子态的共振增强耦合，一种具有长程特性来增强光缔合，另一种具有短程特性来增强对X(0，0)的衰变；(2)磁场中的Feshbach优化光缔合(FOPA)，通过混合X和a态的高能级来极大地提高光缔合率，再次增强波函数的短程特性。对于亚稳态的a(0，0)态，一种新颖的“蓝失谐”光缔合方案可以产生大量的布居，并被用于研究低密度下的纯辐射寿命以及光学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到超冷原子-分子的光缔合。这将产生超冷三原子分子，如Rb3和KRb2，它们处于以前未被探索过的激发态，可以通过激光电离或自电离来检测。对X(0，0)分子的兴趣特别强烈，因为只有在这种量子态下，才能确保碰撞不会因为内部量子态的变化而引起加热。这使得长时间的捕获和对微妙的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极大的兴趣，在足够高的密度下，即使是分子玻色-爱因斯坦凝聚也成为可能。与量子简并气体中的拉曼转移等替代方法相比，该项目中探索的新生产方法在简单性方面提供了巨大的优势，并且它们能够连续或接近连续地产生冷分子。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，为未来对超冷分子和室温分子的研究提供信息。该项目将很好地整合到康涅狄格大学的大型超冷物理项目中，该项目目前有7名教员和大约40名学生和博士后研究员。这种整合的要素包括基于项目的小组会议、指导、研讨会、研讨会以及许多国内和国际合作。我们研究小组成员在当地以及在会议和其他教育机构的发言有助于促进科学理解。更广泛的长期利益包括在超低温化学、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，以及改进的国际合作。

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.