International determination of the Avogadro constant
International determination of the Avogadro constant
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DOI：
10.1088/0026-1394/48/2/e01
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发表时间：
2011-04
期刊：
影响因子：
2.4
通讯作者：
E. Massa;A. Nicolaus
中科院分区：
文献类型：
--
作者：
E. Massa;A. Nicolaus
本期《计量学》收集了一项国际研究项目的论文，该项目旨在通过计算富含同位素28Si的硅晶体中的原子来确定阿伏伽德罗常数NA。50年前，Egidi[1]曾想过实现原子质量标准。1965年，Bonse和Hart操作了第一台x射线干涉仪，从而为Egidi的梦想的实现铺平了道路，不久，Deslattes等人完成了对天然硅晶体中原子的第一次计数。目前的项目由Zosi[4]于1983年提出，于2004年开始，结合了BIPM、INRIM、IRMM、NIST、NPL、NMIA、NMIJ和PTB的经验和能力。由一份谅解备忘录批准的启动信号是一份生产一种富含28Si的硅晶体的合同。浓缩过程由圣彼得堡的机械制造中央设计局负责。随后，在下诺夫哥罗德的俄罗斯科学院高纯度物质化学研究所种植了一种多晶体，在柏林的莱布尼茨研究所<s:1> r kristallz<e:1> chtung种植并纯化了一种28Si晶体。同位素富集使同位素稀释质谱技术得以应用，以前所未有的精度测定阿伏伽德罗常数，实现了埃吉迪的梦想。为了将Egidi的“幻想”付诸实践，澳大利亚精密光学中心制造了两个28Si公斤的准完美球体原型；准确测定了它们的同位素组成、摩尔质量、质量、体积、密度和晶格参数，并在原子尺度上对它们的表面进行了化学和物理表征。Andreas等人的论文回顾了所开展的工作；它整理了所有的发现，并说明了阿伏伽德罗常数是如何得到的。利用红外光谱法测定富集晶体中的杂质浓度和梯度；Zakel等人详细描述了这些测量结果。接下来，Pramann等人说明了如何利用同位素富集和同位素稀释质谱法测量富集晶体的摩尔质量。Valkiers等人报道了重新测量天然硅晶体的摩尔质量，这是由于迫切需要澄清本期给出的NA值与使用天然硅晶体获得的值之间差异的来源而进行的测量。Bulska等人在论文中说明了不同同位素组成测定的一致性分析。正如Massa等人在两篇论文中所报道的那样，为了确定晶格参数，用上述球体之间的材料制造了一个x射线干涉仪。将测量结果与不同晶体样品的晶格比较和杂质梯度相结合，推断出球体的晶格参数。Ferroglio等人的贡献分析了x射线干涉仪的自重变形。Fujimoto等人报道了在日本国家高能物理实验室（KEK）用一种新型自参考衍射仪进行的晶格完美性研究。人们花了很大的努力来描绘球体表面的特征，并校正氧化层和污染原子。这些调查的结果由Busch等人给出。采用光学干涉法测量了球体直径和形貌，达到纳米精度；Bartl等人和Kuramoto等人的论文描述了如何确定球体体积。Andreas等人的论文描述了直径测量的相位修正计算。Picard等人给出了与BIPM、NMIJ和PTB的Pt-Ir标准进行大量比较的结果。本期报告的结果需要完成。必要的活动之一是将28Si原子的质量与其康普顿波长联系起来，以测试质量-能量-频率等效性。另一项工作是监测Pt-Ir原型的稳定性：本问题中描述的技术可以改进和最终确定，通过监测表面演变来计算1千克28Si球体的质量变化，而无需在天平上称重。最后一项活动是使用瓦特天平通过电测量确定28Si球体的质量，而不参考Pt-Ir原型。在这个框架中，有必要证明基于普朗克常数的常规值的千克定义的电学和晶体结构的相互一致性和稳定性。一个相关的问题是制定适当的程序和协议，从新的实现中传播质量单位。由于摩尔普朗克常数是通过测量里德伯常数而众所周知的，因此精确测量NA也提供了精确和独立的普朗克常数h的测定。通过瓦特平衡实验和NA测定得到的普朗克常数值的比较测试了量子力学。事实上，h的瓦特平衡值取决于固体物理，通过约瑟夫森和量子霍尔效应的理论，而从NA得出的h的值取决于原子物理，通过氢和氘的能级差异，其相关的跃迁频率产生关于里德伯常数的信息。感激感谢是写给H-J波尔他出色的项目管理在俄罗斯,中央的K Kaliteevski和他的同事们设计的机械制造和高纯度物质的化学研究所的献身精神和丰富的准时交付材料,到H黎曼和他的工作人员毛皮Kristallzuchtung研究所的晶体生长,我们的导演,他们的建议和财政支持,为他们的日常工作和我们的同事。特别感谢彼得·贝克尔（Peter Becker），在他从德国物理技术研究所（Physikalisch-Technische Bundesanstalt）退休之际，本期特刊献给他。1974年，年轻的Peter加入了PTB的阿伏伽德罗小组，在Peter Seyfried的指导下，跟随Bonse的工作，改进了晶格参数和阿伏伽德罗常数的测量[5,6]。2004年，Peter提出并支持了该项目，承担了风险、管理负担和许多相关活动的协调。参考文献[1]Egidi C 1963质量自然统一的幻想Nature 200 61-2 [1] Bonse U和Hart M 1965 x射线干涉仪应用。理论物理。[科学通报][6][5 - 6][D]等。1974阿伏伽德罗常数的测定。Zosi G 1983原子质量标准的新毕达哥拉斯方法[j]。Becker等，1981硅晶体中（220）晶格平面间距的绝对测量[j]。塞弗里德P等1992，a .阿伏伽德罗常数的测定。B 87 289-98
This issue of Metrologia collects papers about the results of an international research project aimed at the determination of the Avogadro constant, NA, by counting the atoms in a silicon crystal highly enriched with the isotope 28Si. Fifty years ago, Egidi [1] thought about realizing an atomic mass standard. In 1965, Bonse and Hart [2] operated the first x-ray interferometer, thus paving the way to the achievement of Egidi's dream, and soon Deslattes et al [3] completed the first counting of the atoms in a natural silicon crystal. The present project, outlined by Zosi [4] in 1983, began in 2004 by combining the experiences and capabilities of the BIPM, INRIM, IRMM, NIST, NPL, NMIA, NMIJ and PTB. The start signal, ratified by a memorandum of understanding, was a contract for the production of a silicon crystal highly enriched with 28Si. The enrichment process was undertaken by the Central Design Bureau of Machine Building in St Petersburg. Subsequently, a polycrystal was grown in the Institute of Chemistry of High-Purity Substances of the Russian Academy of Sciences in Nizhny Novgorod and a 28Si boule was grown and purified by the Leibniz-Institut für Kristallzüchtung in Berlin. Isotope enrichment made it possible to apply isotope dilution mass spectroscopy, to determine the Avogadro constant with unprecedented accuracy, and to fulfil Egidi's dream. To convey Egidi's 'fantasy' into practice, two 28Si kilogram prototypes shaped as quasi-perfect spheres were manufactured by the Australian Centre for Precision Optics; their isotopic composition, molar mass, mass, volume, density and lattice parameter were accurately determined and their surfaces were chemically and physically characterized at the atomic scale. The paper by Andreas et al reviews the work carried out; it collates all the findings and illustrates how Avogadro's constant was obtained. Impurity concentration and gradients in the enriched crystal were measured by infrared spectroscopy and taken into account; Zakel et al relate these measurements in detail. Next, Pramann et al illustrate how the molar mass of the enriched crystal was measured by exploiting isotopic enrichment and isotope dilution mass spectrometry. Valkiers et al report about remeasurement of the molar mass of a natural Si crystal, a measurement prompted by the exigency of clarifying the origin of the discrepancy between the NA value given in the present issue and the value obtained using natural Si crystals. A consistency analysis of the different isotopic-composition determinations is illustrated in the paper by Bulska et al. As reported in two papers by Massa et al, to determine the lattice parameter an x-ray interferometer was manufactured from the material between the already mentioned spheres. The measurement result was combined with lattice comparisons between different crystal samples and with the impurity gradient to extrapolate the sphere's lattice-parameter. Ferroglio et al's contribution analyzes the self-weight deformation of the x-ray interferometer. Fujimoto et al report about the lattice-perfection investigations carried out by a novel self-referencing diffractometer at the National Laboratory for High-Energy Physics (KEK) in Japan. A really great effort was made to characterize the sphere surfaces and to correct for the oxide layer and the contaminating atoms. The results of these investigations are given by Busch et al. The sphere diameter and topography were measured by optical interferometry to nanometer accuracy; the papers of Bartl et al and Kuramoto et al describe how the sphere volumes were determined. Andreas et al's paper describes the calculation of phase corrections for the diameter measurements. The results of mass comparisons against the Pt–Ir standards of the BIPM, NMIJ and PTB are given by Picard et al. The results reported in the present issue need to be completed. One of the necessary activities is to relate the mass of the 28Si atom to its Compton wavelength to test the mass–energy–frequency equivalence. Another effort is to monitor the stability of the Pt–Ir prototype: the technologies described in the present issue can be refined and finalized to calculate the mass variation of 1 kg 28Si spheres by monitoring the surface evolution without weighing them on a balance. The last activity is the determination of the mass of a 28Si sphere by electrical measurements using a watt balance and without any reference to the Pt–Ir prototype. In this framework, it will be necessary to demonstrate the mutual consistency and the stability of both the electrical and crystal mise en pratique of a kilogram definition based on a conventional value of the Planck constant. A related issue is to develop suitable procedures and protocols to disseminate the unit of mass from the new realizations. Since the molar Planck constant is well known via the measurement of the Rydberg constant, the accurate measurement of NA also provides an accurate and independent determination of the Planck constant, h. A comparison of the values of the Planck constant obtained via the watt-balance experiment and the NA determination tests quantum mechanics. In fact, the watt-balance value of h depends on solid state physics through the theories of Josephson and quantum Hall effects, whereas the value of h derived from NA depends on atomic physics through the energy level differences in hydrogen and deuterium, whose associated transition frequencies yield information on the Rydberg constant. Grateful thanks are addressed to H-J Pohl for his outstanding project management in Russia, to A K Kaliteevski and his colleagues of the Central Design Bureau of Machine Building and the Institute of Chemistry of High-Purity Substances for their dedication and the punctual delivery of the enriched material, to H Riemann and his staff of the Institut für Kristallzüchtung for the crystal growth, to our directors for their advice and financial support, and to our colleagues for their daily work. Special thanks are addressed to Peter Becker, to whom this issue is dedicated on the occasion of his retirement from work at the Physikalisch-Technische Bundesanstalt. In 1974, young Peter joined the PTB's Avogadro group which, under the direction of Peter Seyfried, followed Bonse's work and improved the measurements of the lattice parameter and the Avogadro constant [5, 6]. In 2004, Peter proposed and backed this project by taking on his shoulders the risks, the management burden and the coordination of the many relevant activities. References [1] Egidi C 1963 Phantasies on a natural unity of mass Nature 200 61–2 [2] Bonse U and Hart M 1965 An x-ray interferometer Appl. Phys. Lett. 6 155–6 [3] Deslattes R D et al 1974 Determination of the Avogadro constant Phys. Rev. Lett. 33 463–6 [4] Zosi G 1983 A neo-Pythagorean approach towards an atomic mass standard Lett. Nuovo Cimento 38 577–80 [5] Becker P et al 1981 Absolute measurement of the (220) lattice plane spacing in a silicon crystal Phys. Rev. Lett. 46 1540–3 [6] Seyfried P et al 1992 A determination of the Avogadro constant Z. Phys. B 87 289–98