Eckel Stephen P, Barker Daniel S, Fedchak James A, Scherschligt Julia, Kłos Jacek, Tiesinga Eite
Sensor Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Joint Quantum Institute, College Park, Maryland 20742, US; Department of Physics, University of Maryland, College Park, Maryland, 20742, USA.
Phys Rev A (Coll Park). 2025 Feb;111(2). doi: 10.1103/PhysRevA.111.023317. Epub 2025 Feb 12.
We theoretically investigate the effect of "glancing" collisions on the ultra-high vacuum (UHV) pressure readings of the cold atom vacuum standard (CAVS), based on either ultracold Li or Rb atoms. Here, glancing collisions are those collisions between ultracold atoms and room-temperature background atoms or molecules in the vacuum that do not impart enough kinetic energy to eject an ultracold atom from its trap. Our model is wholly probabilistic and shows that the number of the ultracold atoms remaining in the trap as a function of time is non-exponential. We update the recent results of a comparison between a traditional pressure standard-a combined flowmeter and dynamic expansion system-to the CAVS [D.S. Barker, 035001 (2023)] to reflect the results of our model. We find that the effect of glancing collisions shifts the theoretical predictions of the total loss rate coefficients for Li colliding with noble gases or N by up to 0.6 %. Likewise, we find that in the limit of zero trap depth the experimentally extracted loss rate coefficients for Rb colliding with noble gases or N shift by as much as 2.2 %.
我们从理论上研究了“掠射”碰撞对基于超冷锂或铷原子的冷原子真空标准（CAVS）超高真空（UHV）压力读数的影响。在这里，掠射碰撞是指超冷原子与真空中的室温背景原子或分子之间的碰撞，这些碰撞不会传递足够的动能以将超冷原子从其阱中弹出。我们的模型完全是概率性的，并且表明阱中剩余的超冷原子数量随时间的变化是非指数性的。我们更新了传统压力标准（组合流量计和动态膨胀系统）与CAVS之间比较的最新结果[D.S. 巴克，035001（2023）]，以反映我们模型的结果。我们发现，掠射碰撞的影响使锂与稀有气体或氮气碰撞的总损失率系数的理论预测值最多偏移0.6%。同样，我们发现，在阱深度为零的极限情况下，铷与稀有气体或氮气碰撞的实验提取损失率系数最多偏移2.2%。
