An accurate determination of the Avogadro constant by counting the atoms in a 28Si crystal

TL;DR

This paper presents a highly precise method for determining the Avogadro constant by counting atoms in a silicon crystal, which is crucial for redefining the kilogram based on fundamental constants.

Contribution

It introduces a novel approach using isotope dilution mass spectroscopy to accurately count atoms in a silicon sphere for the first time.

Findings

Avogadro constant determined as 6.02214084(18) x 10^23 mol^-1

Achieved unprecedented accuracy in molar mass measurement

Provides the most accurate input for kilogram redefinition

Abstract

The Avogadro constant links the atomic and the macroscopic properties of matter. Since the molar Planck constant is well known via the measurement of the Rydberg constant, it is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a definition of the kilogram in terms of a fundamental constant. We describe a new approach for its determination by "counting" the atoms in 1 kg single-crystal spheres, which are highly enriched with the 28Si isotope. It enabled isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, 6.02214084(18) x 10^23 mol^-1, is the most accurate input datum for a new definition of the kilogram.