PTB-Physikalisch-Technische Bundesanstalt, Bundesallee 100, 38116 Braunschweig, Germany.
Phys Rev Lett. 2011 Jan 21;106(3):030801. doi: 10.1103/PhysRevLett.106.030801. Epub 2011 Jan 18.
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, NA = 6.022,140,78(18) × 10(23) mol(-1), is the most accurate input datum for a new definition of the kilogram.
阿伏伽德罗常数将物质的原子和宏观性质联系起来。由于摩尔普朗克常数可以通过测量里德伯常数很好地确定，因此它也与普朗克常数密切相关。此外，准确确定阿伏伽德罗常数对于根据基本常数定义千克具有至关重要的意义。我们描述了一种新的方法，通过对 1 千克单晶球中的原子进行计数来确定阿伏伽德罗常数，这些单晶球高度富集了 28Si 同位素。这种方法使得同位素稀释质谱法能够以前所未有的精度确定硅晶体的摩尔质量。所得到的值，NA = 6.02214078(18) × 10(23) mol(-1)，是新的千克定义最准确的输入数据。
