Abstract
This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally. Specifically, we report a quantitative form of the universal, cumulative energy distribution transferred to initially stationary sensor particles by quantum diffractive collisions. The characteristic energy scale corresponds to the localization length associated with the collision-induced quantum measurement, and the shape of the universal function is determined only by the analytic form of the interaction potential at long range. Using cold 87Rb sensor atoms confined in a magnetic trap, we observe experimentally , the universal function specific to van der Waals collisions, and use it to realize a self-defining particle pressure sensor that can be used for any ambient gas. This provides the first primary and quantum definition of the Pascal, applicable to any species and therefore represents a fundamental advance for vacuum and pressure metrology. The quantum pressure standard realized here is compared with a state-of-the-art orifice flow standard transferred by an ionization gauge calibrated for N2. The pressure measurements agree at the 0.5% level.
Highlights
This work demonstrates that quantum diffractive collisions are governed by a universal law characterized by a single parameter that can be determined experimentally
Both theoretically and experimentally, that the low energy behaviour of the cumulative energy distribution imparted to an initially stationary sensor particle embedded in a gas at thermal equilibrium is described by a universal function that depends only on (i) the analytic form of the interaction potential at long-range and (ii) the quantum diffraction energy, Ud ≡ 4mπtσ2 [4]
One of the key results of this work is the theoretical and experimental demonstration that pQDU6 is a universal function with coefficients, βj, that are independent of the short range details of the potential, independent of the strength of the van der Waals interaction, and independent of the masses of the trapped and incident particles
Summary
Vacuum measurement plays a central role in a wide range of scientific and industrial applications including residual gas analysis, semi-conductor device manufacture, and atmospheric modeling. QDU eliminates all of these limitations by enabling the creation of a self-calibrating atomic sensor immune to sensor degradation and applicable to any species, overcoming a long standing and fundamental limitation of existing secondary pressure standards and of ionization based gauges. Researchers at NIST have estimated that they will achieve absolute pressure measurements with an uncertainty of 5% using a combination of trap loss measurements and ab initio calculations of cross-sections for the Li + H2 system They proposed to extend this primary SI traceability to other species using a dynamics gas expansion system [18–20]. In this work we show that it provides a pressure determination at the level of 1% and is applicable for any atomic or molecular species
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