能量天平及千克单位重新定义研究进展

质量单位千克是国际单位制7个基本单位中惟一一个仍以实物定义和复现的基本单位.作为一种实物,其量值必然会因为环境因素及使用时的磨损而发生变化.但由于缺少更高一级的参考标准对其进行考察,国际千克原器的真实变化情况无从得知.国际计量委员会建议采用普朗克常数对千克重新定义,号召各个国家开展普朗克常数的精密测量研究工作,并要求至少有三种独立方案提供有效测量数据.自20世纪70年代起,英、美等国采用功率天平方案进行研究,国际阿伏伽德罗常数合作组织则采用了X射线单晶硅密度的方案.为了应对国际单位制的重大变革,2006年中国计量科学研究院提出了用能量天平法测量普朗克常数的新方案,其特点是可避免国外方案中困难的动态测量.2013年原型实验装置研制成功,证实了能量天平方案原理可行.此后,中国计量科学研究院开始了新一代能量天平装置的研制.2017年5月,中国计量科学研究院提交了普朗克常数的测量结果,不确定度为2.4×10~(-7)(k=1),该数据被国际科学数据委员会收入参考数据库.但由于数据的不确定度尚未进入10~(-8)量级,未被用于普朗克常数的定值.目前中国计量科学研究院正对几项主要的不确定度来源进行研究,预计在未来的两年内达可到10-8量级的不确定度.     

Determination of the Avogadro constant by counting the atoms in a 28Si crystal

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.     

基于三种不同的数据处理软件进行光电效应测普朗克常量实验中的数据处理

运用数据处理软件对物理实验数据进行模拟,避免了繁杂的数学运算过程,增加了数据处理的准确性及快捷性,其程序简单直观,能够直观地反映实验过程及结果,软件知识的运用能够激发学生探索知识的兴趣。本文回顾了光电效应中用反向截止电压法测量普朗克常数的实验原理,讨论了可能影响实验精度的原因,提出了用excel,matlab和origin软件绘制实验曲线确定普朗克常量的方法。     

微机辅助光电效应实验

本介绍一种借助微机研究光电效应的实验系统，微机作为中心控制单元，完成数据采集和存储，实现大量观测数据的建模和平均。最后给出了普朗克常数的测定结果。     

Atom interferometry based on light pulses: Application to the high precision measurement of the ratio <Emphasis Type="Italic">h</Emphasis>/<Emphasis Type="Italic">m</Emphasis> and the determination of the fine structure constant

In this paper we present a short overview of atom interferometry based on light pulses. We discuss different implementations and their applications for high precision measurements. We will focus on the determination of the ratio h/m of the Planck constant to an atomic mass. The measurement of this quantity is performed by combining Bloch oscillations of atoms in a moving optical lattice with a Ramsey-Bordé interferometer.     

光电效应实验分析

分析了光电效应实验中用反向遏止电压法测量普朗克常量的实验原理，讨论了可能影响实验精度的几种电流。     

Physical interpretation of Planck's constant based on the Maxwell theory

The discovery of the Planck relation is generally regarded as the starting point of quantum physics.Planck's constant h is now regarded as one of the most important universal constants.The physical nature of h,however,has not been well understood.It was originally suggested as a fitting constant to explain the black-body radiation.Although Planck had proposed a theoretical justification of h,he was never satisfied with that.To solve this outstanding problem,we use the Maxwell theory to directly calculate the energy and momentum of a radiation wave packet.We find that the energy of the wave packet is indeed proportional to its oscillation frequency.This allows us to derive the value of Planck's constant.Furthermore,we show that the emission and transmission of a photon follows the all-or-none principle.The "strength" of the wave packet can be characterized by ζ,which represents the integrated strength of the vector potential along a transverse axis.We reason that ζ should have a fixed cut-off value for all photons.Our results suggest that a wave packet can behave like a particle.This offers a simple explanation to the recent satellite observations that the cosmic microwave background follows closely the black-body radiation as predicted by Planck's law.     

利用色散法探索玻尔氢原子理论测量普朗克常数

普朗克常数是物理学中一个重要的常数,利用测角仪器分光计,探索用玻尔氢原子理论来测普朗克常数。根据最小偏向角测量三棱镜折射率的原理,利用分光计测量三棱镜的折射率来研究光的色散规律,测量棱镜材料对不同波长入射光的折射率,得到棱镜材料的色散曲线和拟合方程。根据玻尔的氢原子理论,用分光计测出氢原子光谱四条谱线（α,β,γ,δ）的偏向角对应的折射率,由科西经验公式计算出相应的波长。     

Determination of the Planck constant by means of a watt balance

The kilogram is the only base unit of the Système International d’unités (SI) still defined by a material artefact. Regarding the past evolution of the SI and the poor knowledge of the stability of the international prototype, its definition is not satisfactory. In the long term, it would be better to move to a definition based either on atomic properties or on fundamental constants. Among the various researches in progress in metrology laboratories, one of the most promising ways seems to be the watt balance. Its principle consists in comparing a mechanical power to an electromagnetic power. This comparison results from a measurement performed in two steps: a static measurement during which the Laplace force acting on a coil driven by a DC current and subjected to an induction field is compared to the weight of a standard mass, and a dynamic measurement where the induced voltage at the terminals of the same coil is determined when it is moved in the same field at a known velocity. The measurement of electrical quantities in terms of the Josephson and the quantum Hall effects then allows the mass unit be linked to the Planck constant. Although the principle of the experiment remains simple and direct, obtaining sufficiently low uncertainty ( 10^-8) implies that devices relevant of various fields of physics must be implemented at their best level. In this paper, a review of the present developments at international level is presented.     

The Planck Constant for the Definition and Realization of the Kilogram

On May 20, 2019 the values of the Planck, h, and Avogadro, N_A, constants will be fixed, revising our measurement system, the International System of Units (SI), and providing a new way to get mass traceability. While the famous energy relations mc² and hf may remind many that the Planck constant is indeed related to mass, it is less recognized how this is also true for the Avogadro constant. These concepts are reviewed in the context of the upcoming revision of the SI. How the fixed values were chosen and how mass traceability will be maintained with the smallest uncertainty are also discussed.     

质量单位千克定义的历史、现状和发展趋势

自1889年以来,千克的国际原器作为国际单位制(SI)质量单位的定义。这是SI定义基本单位最后一个人工制造的基准,它的重新定义必将影响着几个其他基本单位。文章介绍了瓦特天平的工作原理以及普朗克常数的实验测定。这些结果对物理学和计量学具有重要的意义。     

用白炽灯作光源测量普朗克常量--第36届国际奥林匹克物理竞赛实验题分析

介绍了第36届国际奥林匹克物理竞赛“用白炽灯测量普朗克常量”实验,该题利用白炽灯作为辐射源并配合波长滤波器、减光板以及光敏电阻等装置,测量普朗克常量.文章对该实验进行了分析并给出解答.     

趋近平均法测量普朗克常量

为解决光电效应实验中的测量误差较大问题,提出了“趋近平均法”对普朗克常量进行测量,可使测量误差由使用拐点法的34%降至13.5%.     

万有引力常数G精确测量实验进展

万有引力常数G是人类历史上引入的第一个基本物理学常数,其在理论物理、天体物理和地球物理等许多领域中扮演着重要角色.两百多年来,人们共测量出了200多个G值,但G的测量精度仍然是所有物理学常数中最差的,这一现象反映了测G工作本身的复杂性和困难性.本文简要概述了G值测量的意义和测G的历史,并结合自2010年以来国际上新出现的三个高精度测G实验介绍这一领域的研究进展,以及华中科技大学引力实验中心测G工作的最新动态.     

A Note on Black Hole Information Paradox in de Sitter Spacetimes

The possibility of stable or quasi-stable Planck mass black hole remnants as solution to the black hole information paradox is commonly believed phenomenologically unacceptable. Since we need a black hole remnant for every possible initial state,the number of remnants is expected to be infinite and that would lead to remnant pair production in any physical process with a total available energy roughly exceeding the Planck mass. In this note I point out that a positive cosmological constant of the Universe would naturally lead to an upper bound on the numberof possible remnants.     

原子钟在精密测量领域的新应用

近年来,伴随着原子钟研制精度的不断提高,尤其是基于中性原子的光晶格钟,其稳定度已经推进到10^-19量级,不确定度也已达到小系数10^-18量级,原子光钟在精密测量领域的应用也被推上了一个新高度。除了被广泛谈及的用于测量精细结构常数的变化、测量引力波以及寻找暗物质,高精度的原子光钟被认为是一个可用于大地测量以及爱因斯坦广义相对论验证的强有力的工具。文章主要从原子光晶格钟测量引力红移的角度出发,介绍原子光晶格钟在测地学方面的应用。最后,引入高精度原子光晶格钟用于系统熵的测量,这可能成为未来精密测量的一个新领域。     

New determination of the fine structure constant and test of the quantum electrodynamics

We report a new measurement of the ratio h/m(Rb) between the Planck constant and the mass of (87)Rb atom. A new value of the fine structure constant is deduced, α(-1)=137.035999037(91) with a relative uncertainty of 6.6×10(-10). Using this determination, we obtain a theoretical value of the electron anomaly a(e)=0.00115965218113(84), which is in agreement with the experimental measurement of Gabrielse [a(e)=0.00115965218073(28)]. The comparison of these values provides the most stringent test of the QED. Moreover, the precision is large enough to verify for the first time the muonic and hadronic contributions to this anomaly.     

普朗克常量测定仪的改进

对普朗克常量测定仪的电路部分进行了改造,采用由三端可调稳压器LM317和LM337组成的正负双电源电路,用运算放大器OPA128LM作为电流-电压转换器,电流测量范围可达10-8~10-14A,并总结了在实际电路设计和制作中,提高仪器精度和稳定性的方法.     

The Avogadro Constant for the Definition and Realization of the Mole

The International System of Units’ (SI) base unit of the quantity “amount of substance” is the mole (symbol: mol). After the revision of the SI to be implemented in 2019, when all SI units will be based solely on constants, the mole will be defined through a fixed value of the Avogadro constant N_A. One mole contains exactly 6.02214076 × 10²³ elementary entities, meaning the mole will no longer be linked to the kilogram. Currently, the mole is defined via the mass of exactly 0.012 kg of the ¹²C isotope which links it to the kilogram prototype. The history, changes, and implications of the revised definition of the mole are discussed here from the chemist's point of view. The ability to count entities such as atoms or molecules (precisely enough to enable a revision of the SI and preserve consistency of previous and future measurements) is crucial. This is achieved with the realization (Mise en Pratique) based on the X‐ray‐crystal density (XRCD) method (counting the atoms in a silicon sphere). The determination of N_A, focusing on the measurement of the molar mass of silicon highly enriched in the ²⁸Si isotope, with the lowest uncertainty so far, is presented.     

Covariant formulation of non-equilibrium statistical thermodynamics

The Fokker Planck equation is considered as the master equation of macroscopic fluctuation theories. The transformation properties of this equation and quantities related to it under general coordinate transformations in phase space are studied. It is argued that all relations expressing physical properties should be manifestly covariant, i.e. independent of the special system of coordinates used. The covariance of the Langevin-equations and the Fokker Planck equation is demonstrated. The diffusion matrix of the Fokker Planck equation is used as a contravariant metric tensor in phase space. Covariant drift vectors associated to the Langevin- and the Fokker Planck equation are found. It is shown that special coordinates exist in which the covariant drift vector of the Fokker Planck equation and the usual non-covariant drift vector are equal.The physical property of detailed balance and the equivalent potential conditions are given in covariant form. Finally, the covariant formulation is used to study how macroscopic forces couple to a system in a non-equilibrium steady state. A general fluctuation-dissipation theorem for the linear response to such forces is obtained.