Istituto Nazionale di Ricerca Metrologica (INRIM) , Strada delle Cacce 91, 10135 Torino, Italy.
Department of Chemistry, University of Pavia , Via Taramelli 12, 27100 Pavia, Italy.
Anal Chem. 2016 Jul 5;88(13):6881-8. doi: 10.1021/acs.analchem.6b01537. Epub 2016 Jun 23.
At present, counting atoms in a one-kilogram sphere made of (28)Si-enriched silicon allows the determination of the Avogadro constant with the 2.0 × 10(-8) relative standard uncertainty required for the realization of the definition of the new kilogram. With the exception of carbon, oxygen, boron, nitrogen, and hydrogen, the claimed uncertainty is based on the postulation that the silicon material used to manufacture the sphere was above a particular level of purity. Two samples of the silicon were measured using instrumental neutron activation analysis to collect experimental data to test the purity assumption. The results obtained in two experiments carried out using different research reactor neutron sources are reported. The analysis confirmed that the silicon material was of sufficient purity by quantifying the ultratrace concentration of 12 elements and determining the detection limits of another 54 elements.
目前，通过对一个由（28）Si 富集硅制成的一千克球体中的原子进行计数，可以以实现新千克定义所需的 2.0×10(-8)相对标准不确定度来确定阿伏伽德罗常数。除了碳、氧、硼、氮和氢之外，所声称的不确定度基于这样一个假设，即用于制造球体的硅材料的纯度高于特定水平。使用仪器中子活化分析对两种硅样品进行了测量，以收集实验数据来检验纯度假设。报告了使用两个不同的研究堆中子源进行的两个实验的结果。通过定量分析 12 种微量元素的超痕量浓度和确定另外 54 种元素的检测限，分析确认了硅材料的纯度达到了足够的水平。
