Cold alkali atoms as sensors of ultra-high vacuum: theoretical calculations of collision induced losses

New Cold-Atom- Vacuum-Sensors (CAVS)¹ are being developed at the National Institute of Science and Technology with the goal to measure ultra-high vacuum pressures less than 10−9 torr and to establish pressure standard based on quantum phenomena. The sensor is based on a cloud of laser-cooled and trapped ⁷Li(²S) or ⁸⁷Rb(²S) alkali atoms held at μK temperatures connected to the vacuum chamber containing residual gases at room temperature. These residual gases collide with the trapped atomic cloud which results in cold atom losses that can be measured. To support these experimental efforts we perform quantum scattering calculations² using computed state-of-the-art ab initio potentials to determine these rate coefficients and their uncertainties for collisions of trapped Li/Rb with residual vacuum chamber gases such as: Rare Gases, N₂, H₂ and new efforts on other polyatomic gases such as CO₂, CO(¹Σ) and O₂(³Σ⁻_g). The computed rate coefficients for Rare Gases, N₂ and H₂ are in good accord with CAVS experiments³.

1. L. Ehinger, B. P. Acharya et al. AVS Quant. Sci. 4, 034403 (2022)

2. J. Kłos and E. Tiesinga J. Chem. Phys. 158, 014308 (2023)

3. D. S. Barker, J. A. Fedchak, et al. AVS Quant. Sci. 5, 035001 (2023)