2024/09/17 by Stephen Eckel, Eckel, Stephen P., Daniel S. Barker +9
Decision Sciences · Physics and Astronomy · #Advanced Frequency and Time Standards #Atomic Physics (physics.atom-ph) #FOS: Physical sciences #Radioactive Decay and Measurement Techniques #Scientific Measurement and Uncertainty Evaluation
paper · pdf · doi:10.48550/arxiv.2409.11226
openalex publication_date 2024/09/17 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
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 7Li or 87Rb 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, et al., arXiv:2302.12143] 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 7Li colliding with noble gases or N2 by up to 0.6 %. Likewise, we find that in the limit of zero trap depth the experimentally extracted loss rate coefficients for 87Rb colliding with noble gases or N2 shift by as much as 2.2 %.