Creating ultra-cold molecules by sympathetic cooling

激光冷却在探索捕获原子之间的超冷相互作用、量子原子光学以及通过高分辨率光谱进行精密计量方面具有重要意义。它还为凝聚态物理和最近的量子信息提供了一个控制良好的试验场。现在人们的注意力转向了分子，因为在超冷分子之间可能发生完全不同的相互作用。它们被视为寻找CPT违逆、探索超冷化学以及利用偶极分子创造新型量子流体的理想候选者。不幸的是，激光冷却对许多原子物种都非常成功，但它不能应用于分子，因此需要新的方法来达到分子和超冷物理的这种新状态。该方案旨在解决这一问题，通过利用交感和蒸发冷却的非常普遍的技术，从由光学斯塔克减速产生的冷静止分子中产生超冷分子。为了进行这项工作，我们将在10 mK到1 K的温度范围内，将超冷激光冷却的氙原子与静止的冷分子进行热接触。我们将利用冷氙原子和被困在光场中的分子之间的弹性碰撞来加热混合物，使其达到低于目前存在的1 mK瓶颈的普通温度。虽然原则上同情冷却和蒸发冷却适用于许多分子种类，但本项目将探索通过与超冷氙碰撞来冷却氢分子和苯分子，产生100微开尔文及以下温度范围的分子。该计划的一个重要部分将是通过实验和理论研究原子-分子碰撞，这对交感和蒸发冷却以及一旦分子冷却到微开尔文温度范围后可以研究的潜在超冷分子化学至关重要。这项研究将利用我们的光学斯塔克减速机，并将建立一个磁光阱来产生超冷氙原子。我们还将建立一个深光学陷阱，它将能够长时间（秒）保持原子或分子物种的热化。

Laser cooling has been of primary importance in the exploration of ultra-cold interactions between trapped atoms, for quantum atom optics, and for precision metrology through high-resolution spectroscopy. It has also provided a well-controlled testing ground for condensed matter physics, and more recently quantum information. Attention has now turned to molecules because of the quite different interactions that can occur between ultra-cold molecules. They are seen as ideal candidates in the search for CPT violation, for exploring ultra-cold chemistry, and for the creation of novel quantum fluids using dipolar molecules. Unfortunately, laser cooling, which has been so successful for many atomic species cannot be applied to molecules and thus new methods are required to reach this new regime in molecular and ultra-cold physics. This proposal aims address this problem by utilising the very general techniques of sympathetic and evaporative cooling to create ultra-cold molecules from cold stationary molecules that have been created by optical Stark deceleration. To undertake this work we will bring ultra-cold laser cooled xenon atoms into thermal contact with stationary cold molecules initially at temperatures in the 10 mK to 1 K range. We will use elastic collisions between the cold xenon atoms and the molecules co-trapped within an optical field to thermalise the mixture, bringing it to a common temperature below the 1 mK bottleneck that currently exists. Although in principle sympathetic and evaporative cooling are applicable to many molecular species, this project will explore the cooling of molecular hydrogen and benzene by collisions with ultra cold xenon, producing molecules in the 100 microkelivn temperature range and below. An important part of this programme will be the study, via experiment and theory, the atom-molecule collisions that are vitally important for sympathetic and evaporative cooling, as well as for the potential ultra-cold molecular chemistry that can be studied once the molecules are cooled into the microkelvin temperature regime. This research will utilise our optical Stark decelerator and will build a magneto-optical trap for producing ultra-cold xenon atoms. We will also build a deep optical trap that will be capable of holding atomic or molecular species for the long periods (seconds) required for thermalisation.