Accurate measurement of the loss rate of cold atoms due to background gas collisions for the quantum-based cold atom vacuum standard

Abstract

We present measurements of thermalized collisional rate coefficients for ultra-cold ${}^7$Li and ${}^{87}$Rb colliding with room-temperature He, Ne, N${}_2$, Ar, Kr, and Xe. In our experiments, a combined flowmeter and dynamic expansion system, a vacuum metrology standard, is used to set a known number density for the room-temperature background gas in the vicinity of the magnetically trapped ${}^7$Li or ${}^{87}$Rb clouds. Each collision with a background atom or molecule removes a ${}^7$Li or ${}^{87}$Rb atom from its trap and the change in the atom loss rate with background gas density is used to determine the thermalized loss rate coefficients with fractional standard uncertainties better than 1.6 % for ${}^7$Li and 2.7 % for ${}^{87}$Rb. We find consistency -- a degree of equivalence of less than one -- between the measurements and recent quantum-scattering calculations of the loss rate coefficients [J. Klos and E. Tiesinga, J. Chem. Phys. 158, 014308 (2023)], with the exception of the loss rate coefficient for both ${}^7$Li and ${}^{87}$Rb colliding with Ar. Nevertheless, the agreement between theory and experiment for all other studied systems provides validation that a quantum-based measurement of vacuum pressure using cold atoms also serves as a primary standard for vacuum pressure, which we refer to as the cold-atom vacuum standard.

12 pages, 4 figures, 3 tables, 2 appendices

References in corpus (3)

• Development of a new UHV/XHV pressure standard (cold atom vacuum standard)
• Observation of quantum diffractive collisions using shallow atomic traps
• Cross-calibration of atomic pressure sensors and deviation from quantum diffractive collision universality for light particles

Cited by in corpus (6)

• Collision-resolved pressure sensing
• Trapped particle evolution driven by residual gas collisions
• On the effect of "glancing" collisions in the cold atom vacuum standard
• Accurate, precise pressure sensing with tethered optomechanics
• Boundaries of universality of thermal collisions for atom-atom scattering
• Invariance of quantum scattering rate coefficients to anisotropy of atom-molecule interactions