Interactions of anions with ultacold atoms in a hybrid trap

超冷温度范围内的分子和分子离子为研究冷碰撞、反应动力学或量子化学等基本现象开辟了新的视角，并在以下方面找到了广泛的令人兴奋的应用：高精度光谱学或量子计算。在过去的十年中，已经开发了越来越多的技术用于在超冷温度范围内制备或创建分子样品。然而，仍然缺乏将分子阴离子冷却到毫开尔文状态的有效方法。本项目旨在研究超冷原子与负分子离子的相互作用动力学。具体来说，我们的主要目标是证明在与激光冷却原子碰撞的分子阴离子的共振冷却。我们将探索和扩展方法，以确定运动和内部能量分布的被困离子，特别是光剥离光谱和断层扫描。我们试图测量原子-分子阴离子体系中不同反应通道的速率系数，以扩展对涉及带负电荷分子的超冷反应动力学的理解，使用混合原子-离子阱（HAITrap）是实现这一目标的理想实验平台，因为它将存储在射频（rf）阱中的离子与光学捕获的超冷原子在高度可控的条件下结合起来。我们最近建立了一个新的HAITrap组成的八极射频线性离子阱结合暗自发力光阱（darkSPOT）的超冷原子。在这个研究建议的框架内，我们将研究系统OH- + Rb作为一个原型系统，了解分子阴离子和超冷原子之间的弹性和非弹性相互作用。由于其在无机、有机和大气化学中的基本作用，分子阴离子OH-是研究反应动力学基本问题的非常合适的测试系统。组合系统OH- + Rb似乎是有利的交感冷却的内部和运动的自由度的分子阴离子，这在原则上，应该允许在绝对旋转和振动基态的准备。然后，我们将实验扩展到更复杂的多原子分子阴离子，特别是水合水簇OH-（H2O）n，以解决从气体到凝聚相环境的转变，以及另一种原型分子阴离子SF6-。该项目建立在德国海德堡大学和奥地利因斯布鲁克大学两个小组之间的良好合作基础上，结合他们在超冷量子气体物理学、离子捕获和分子反应动力学方面的互补专业知识。

Molecules and molecular ions in the ultracold temperature regime open new perspectives for the investigation of fundamental phenomena such as cold collisions, reactive dynamics or quantum chemistry, and also find a wide range of exciting applications in, e.g., high precision spectroscopy or quantum computation. During the last decade, an increasing number of techniques have been developed for preparing or creating molecular samples in the ultracold temperature regime. Nevertheless, an efficient method for cooling molecular anions into the millikelvin regime is still lacking. The present project aims at the investigation of the interaction dynamics between ultracold atoms and negative molecular ions. Specifically, our main goal is to demonstrate sympathetic cooling of molecular anions in collisions with laser-cooled atoms. We will explore and expand methods to determine motional and internal energy distributions of trapped ions, in particular photodetachment spectroscopy and tomography. We seek to measure rate coefficients of different reactive channels in atom-molecular anion systems for an extended understanding of ultracold reaction dynamics involving negatively charged molecules.The use of a hybrid atom-ion trap (HAITrap) is the ideal experimental platform for achieving this goal since it combines ions stored in an radiofrequency (rf) trap with optically trapped ultracold atoms under highly controllable conditions. We have recently set up a novel HAITrap consisting on an octupole rf linear trap for ions combined with a Dark Spontaneous Force Optical Trap (darkSPOT) for ultracold atoms. Within the framework of this research proposal we will investigate the system OH- + Rb as a prototypical system for understanding elastic and inelastic interactions between molecular anions and ultracold atoms. Due to its fundamental role in inorganic, organic and atmospheric chemistry, the molecular anion OH- is a well-suited test system for studying fundamental questions concerning reaction dynamics. The combined system OH- + Rb appears to be advantageous for sympathetic cooling of the internal and motional degrees of freedom of the molecular anions, which, in principle, should allow preparation in the absolute rotational and vibrational ground state. We will then extend the experiment to more complex polyatomic molecular anions, in particular hydrated water clusters OH-(H2O)n to address the transition from gas to condensed phase environments, and another prototypical molecular anion, SF6-.This project builds upon the well-established collaboration between the two groups at the University of Heidelberg, Germany, and the University of Innsbruck, Austria, repectively, combining their mutually complementary expertise in the physics of ultracold quantum gases, ion trapping and molecular reaction dynamics.