Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

TL;DR

This paper reports improved measurement results for the Avogadro constant using isotopically enriched silicon spheres, achieving high precision necessary for redefining the kilogram.

Contribution

It presents new measurement techniques and refined results for the Avogadro constant based on 28Si-enriched crystals, enhancing accuracy for fundamental constant determination.

Findings

Avogadro constant measured as 6.02214076(12)×10^{23} mol^{-1}

Achieved target relative uncertainty of 2.0×10^{-8}

Validated the X-ray crystal density method for high-precision measurements

Abstract

New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of $N_A = 6.022 140 76(12) \times 10^{23}$ mol$^{-1}$. The X-ray crystal density method has thus achieved the target relative standard uncertainty of $2.0 \times 10^{-8}$ necessary for the realization of the definition of the new kilogram.