Interactions of anions with ultacold atoms in a hybrid trap

分子和分子离子在超低温下为冷碰撞、反应动力学或量子化学等基本现象的研究开辟了新的视角，并在高精度光谱或量子计算等领域找到了令人兴奋的广泛应用。在过去的十年里，越来越多的技术被开发出来，用于在超低温条件下制备或创建分子样品。然而，仍然缺乏一种有效的方法将分子阴离子冷却到Millikelvin区域。本项目旨在研究超冷原子与负分子离子之间的相互作用动力学。具体地说，我们的主要目标是演示分子阴离子在与激光冷却原子的碰撞中的共鸣冷却。我们将探索和扩展确定俘获离子的运动和内能分布的方法，特别是光分离光谱和层析成像。我们试图测量原子-分子阴离子系统中不同反应通道的速率系数，以扩展对涉及负电荷分子的超冷反应动力学的理解。混合原子-离子陷阱(HAITrap)的使用是实现这一目标的理想实验平台，因为它将存储在射频陷阱中的离子与高度可控条件下的光学捕获的超冷原子结合在一起。我们最近建立了一种新型的HAITrap，它由一个八极射频离子线性陷阱和一个暗自发力光陷阱(暗斑)组成，用于超冷原子。在这个研究方案的框架内，我们将研究OH-+Rb体系作为理解分子阴离子和超冷原子之间弹性和非弹性相互作用的原型系统。由于其在无机、有机和大气化学中的基础作用，分子阴离子OH-是研究与反应动力学有关的基本问题的非常合适的测试系统。组合体系OH-+Rb似乎有利于分子阴离子内部和运动自由度的交感冷却，原则上这应该允许在绝对转动和振动基态下进行准备。然后，我们将把实验扩展到更复杂的多原子分子阴离子，特别是水合水团簇OH-(H2O)n，以解决从气体到凝聚相环境的转变，以及另一个典型的分子阴离子SF6-。这个项目分别建立在德国海德堡大学和奥地利因斯布鲁克大学这两个小组之间良好的合作基础上，结合了他们在超冷量子气体物理、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.