近日，北京大学的陈徐宗&袁骁及其研究团队取得一项新进展。经过不懈努力，他们成功建立微重力条件下捕获原子蒸发冷却的动力学方程。相关研究成果已于2024年4月16日在国际知名学术期刊《物理评论A》上发表。

在文本中，为了研究原子在空间站微重力环境下的蒸发和冷却过程，研究人员建立了捕获原子蒸发冷却的动力学方程，并得到了原子温度与捕获激光参数和重力加速度的解析表达式。在此模型中，原子的蒸发过程被巧妙地类比为对捕获原子施加的阻尼力，从而使得被捕获原子的蒸发冷却过程可以形象地，理解为光学偶极子阱中被捕获原子的阻尼振荡。

进一步地，通过在模型中引入重力因素，研究人员成功建立了冷却后温度随重力变化的解析模型，理论结果与铷-87原子在地面上的蒸发实验结果吻合较好。

理论研究表明，在空间站的微重力环境下，相较于地面原子蒸发冷却实验，当忽略由背景气体碰撞导致的一体损失以及原子间非弹性碰撞引发的三体复合损失等原子损失时，有望实现更低温的原子气体。

附：英文原文

Title: Dynamic equation for evaporative cooling of trapped atoms in microgravity

Author: Xiao-long Yuan, Jiachen Yu, Hui Li, Biao Wu, Wei Xiong, Xiaoji Zhou, Xuzong Chen

Issue&Volume: 2024/04/16

Abstract: In this paper, to investigate how atoms evaporate and cool in microgravity environments of the space station, we have developed the dynamic equation for evaporative cooling of trapped atoms and obtained the analytical expression of atomic temperature with respect to trapping laser parameters and gravitational acceleration. In our model, the evaporation of atoms is equivalent to applying a damping force to the trapped atoms, and the evaporative cooling process of trapped atoms is comprehended as the damped oscillation of trapped atoms in the optical dipole traps. By introducing the gravity in our model, we obtained the analytical model of temperature variation with gravity after cooling, and the theoretical results agree well with the evaporation experiment of rubidium-87 atoms on the ground. Our theoretical results show that, compared with the atomic evaporative cooling experiment on the ground, the microgravity environment of the space station can achieve cooler atomic gases when the losses of atoms, such as the one-body loss caused by background-gas collisions and the three-body recombination loss caused by interatomic inelastic collisions, can be ignored.

DOI: 10.1103/PhysRevA.109.043315

Source: https://journals.aps.org/pra/abstract/10.1103/PhysRevA.109.043315