scholarly journals The Avogadro constant: determining the number of atoms in a single-crystal 28 Si sphere

2011 ◽  
Vol 369 (1953) ◽  
pp. 3925-3935 ◽  
Author(s):  
Peter Becker ◽  
Horst Bettin
Keyword(s):  
Single Crystal ◽  
Accurate Determination ◽  
Silicon Crystal ◽  
Fundamental Constant ◽  
Planck Constant ◽  
Amount Of Substance ◽  
Avogadro Constant ◽  
Unique Approach ◽  
Definition Of ◽  
Si Isotope

The Avogadro constant, the number of entities in an amount of substance of one mole, links the atomic and the macroscopic properties of matter. Since the molar Planck constant—the product of the Planck constant and the Avogadro constant—is very well known via the measurement of the Rydberg constant, the Avogadro constant is also closely related to the Planck constant. In addition, its accurate determination is of paramount importance for a new definition of the kilogram in terms of a fundamental constant. Here, we describe a new and unique approach to determine the Avogadro constant from the number of atoms in 1 kg single-crystal spheres that are highly enriched with the 28 Si isotope. This approach has enabled us to apply isotope dilution mass spectroscopy to determine the molar mass of the silicon crystal with unprecedented accuracy. The value obtained, N A =6.022 140 82(18)×10 23  mol −1 , is now the most accurate input datum for a new definition of the kilogram.

scholarly journals A critical review of the proposed definitions of fundamental chemical quantities and their impact on chemical communities (IUPAC Technical Report)

2017 ◽  
Vol 89 (7) ◽  
pp. 951-981 ◽  
Author(s):  
Roberto Marquardt ◽  
Juris Meija ◽  
Zoltan Mester ◽  
Marcy Towns ◽  
Ron Weir ◽  
...  
Keyword(s):  
Critical Review ◽  
Planck Constant ◽  
Amount Of Substance ◽  
Work Related ◽  
Avogadro Constant ◽  
Technical Report ◽  
Measurements In Chemistry ◽  
Definition Of ◽  
New Si

AbstractIn the proposed new SI, the kilogram will be redefined in terms of the Planck constant and the mole will be redefined in terms of the Avogadro constant. These redefinitions will have some consequences for measurements in chemistry. The goal of the Mole Project (IUPAC Project Number 2013-048-1-100) was to compile published work related to the definition of the quantity ‘amount of substance’, its unit the ‘mole’, and the consequence of these definitions on the unit of the quantity mass, the kilogram. The published work has been reviewed critically with the aim of assembling all possible aspects in order to enable IUPAC to judge the adequateness of the existing definitions or new proposals. Compilation and critical review relies on the broadest spectrum of interested IUPAC members.

Measurement of the molar mass of the 28Si-enriched silicon crystal (AVO28) with HR-ICP-MS

2015 ◽  
Vol 30 (12) ◽  
pp. 2449-2458 ◽  
Author(s):  
Tongxiang Ren ◽  
Jun Wang ◽  
Tao Zhou ◽  
Hai Lu ◽  
Yuan-jing Zhou
Keyword(s):  
Crucial Role ◽  
Molar Mass ◽  
Mass Measurement ◽  
Accurate Determination ◽  
Silicon Crystal ◽  
Avogadro Constant ◽  
Icp Ms ◽  
Definition Of

Accurate molar mass measurement of the highly 28Si-enriched crystal (AVO28) plays a crucial role in the accurate determination of the Avogadro constant and thus the new definition of the kilogram.

scholarly journals The watt balance: determination of the Planck constant and redefinition of the kilogram

2011 ◽  
Vol 369 (1953) ◽  
pp. 3936-3953 ◽  
Author(s):  
M. Stock
Keyword(s):  
International System ◽  
Accurate Determination ◽  
Electrical Power ◽  
Planck Constant ◽  
System Of Units ◽  
Macroscopic Quantum Effects ◽  
Watt Balance ◽  
Definition Of ◽  
Base Units

Since 1889, the international prototype of the kilogram has served as the definition of the unit of mass in the International System of Units (SI). It is the last material artefact to define a base unit of the SI, and it influences several other base units. This situation is no longer acceptable in a time of ever-increasing measurement precision. It is therefore planned to redefine the unit of mass by fixing the numerical value of the Planck constant. At the same time three other base units, the ampere, the kelvin and the mole, will be redefined. As a first step, the kilogram redefinition requires a highly accurate determination of the Planck constant in the present SI system, with a relative uncertainty of the order of 1 part in 10 8 . The most promising experiment for this purpose, and for the future realization of the kilogram, is the watt balance. It compares mechanical and electrical power and makes use of two macroscopic quantum effects, thus creating a relationship between a macroscopic mass and the Planck constant. In this paper, the operating principle of watt balance experiments is explained and the existing experiments are reviewed. An overview is given of all available experimental determinations of the Planck constant, and it is shown that further investigation is needed before the redefinition of the kilogram can take place. Independent of this requirement, a consensus has been reached on the form that future definitions of the SI base units will take.

The molar mass of a new enriched silicon crystal: maintaining the realization and dissemination of the kilogram and mole in the new SI

2019 ◽  
Vol 88 (2) ◽  
pp. 20904 ◽  
Author(s):  
Axel Pramann ◽  
Olaf Rienitz
Keyword(s):  
Inductively Coupled Plasma ◽  
Molar Mass ◽  
Silicon Crystal ◽  
Isotope Ratio Mass Spectrometry ◽  
Amount Of Substance ◽  
Inductively Coupled ◽  
Crystal Density ◽  
Combined Uncertainty ◽  
Si Isotope ◽  
Silicon Spheres

The local distribution of the isotopic composition and molar mass M of a new silicon crystal (Si28-24Pr11) highly enriched in the 28Si isotope is reported, with focus on the experimental methods as well as on the associated uncertainties. The crystal was used in 2018 for the production of two additional silicon spheres for the realization and verification of the Avogadro constant NA using the “X-ray-crystal-density (XRCD) method” which is a primary method for the dissemination of the revised SI units mole and kilogram. 17 subsamples have been investigated (from five different axial and in several radial positions) by isotope ratio mass spectrometry using a multicollector-inductively coupled plasma mass spectrometer (MC-ICP-MS). The average molar mass of the crystal is M = 27.976 933 787(77) g/mol with a relative combined uncertainty uc,rel(M) = 2.7 × 10−9. The mean amount-of-substance fraction of 28Si is x(28Si) = 0.999 993 104 (66) mol/mol indicating that this crystal has the highest enrichment in this isotope which has ever been used for the determination of NA. No local variations in M and x(iSi) (i = 28, 29, and 30) could be identified due to material properties. The results are compared with those from two previous enriched crystals.

scholarly journals On the five base quantities of nature and SI (The International System of Units)

2011 ◽  
Vol 47 (2) ◽  
pp. 241-246
Author(s):  
G. Kaptay
Keyword(s):  
International System ◽  
Fundamental Constant ◽  
Fundamental Constants ◽  
Planck Constant ◽  
Amount Of Substance ◽  
Substance Mole ◽  
System Of Units ◽  
Elementary Charge ◽  
Base Units ◽  
Constants Of Nature

It is shown here that five base quantities (and the corresponding five base units) of nature are sufficient to define all derived quantities (and their units) and to describe all natural phenomena. The base quantities (and their base units) are: length (m), mass (kg), time (s), temperature (K) and electric charge (C). The amount of substance (mole) is not taken as a base quantity of nature and the Avogadro constant is not considered as a fundamental constant of nature, as they are both based on an arbitrary definition (due to the arbitrary value of 0.012 kg for the mass of 1 mole of C-12 isotope). Therefore, the amount of substance (mole) is moved from the list of base quantities to the category of the supplementary units (to be re-created after its abrogation in 1995). Based on its definition, the luminous intensity (cd) is not a base quantity (unit), therefore it is moved to the list of derived quantities (units). The ampere and coulomb are exchanged by places in the list of base and derived units, as ampere is a speed of coulombs (but SI defines meter, not its speed as a base unit). The five base quantities are re-defined in this paper by connecting them to five fundamental constants of nature (the most accurately known frequency of the hydrogen atom, the speed of light, the Planck constant, the Boltzmann constant and the elementary charge) with their numerical values fixed in accordance with their CODATA 2006 values (to be improved by further experiments).

Revision of the SI: The Determination of the Avogadro Constant as the Base for the Kilogram

2014 ◽  
Vol 613 ◽  
pp. 3-10 ◽  
Author(s):  
Arnold Nicolaus ◽  
Horst Bettin ◽  
Michael Borys ◽  
Ulrich Kuetgens ◽  
Axel Pramann
Keyword(s):  
International System ◽  
Fundamental Constant ◽  
Lattice Parameter ◽  
Planck Constant ◽  
Avogadro Constant ◽  
System Of Units ◽  
Working Groups ◽  
Fixed Constant ◽  
Watt Balance

At least four units of the International System of Units (SI) are on the way to a new definition. Especially for the unit of mass, the kilogram, a rigorous change is considered. Instead of the current definition, a 1kg-artifact in form of a Pt-Ir-cylinder, the intended formulation relates the unit of mass to a fundamental constant. In detail this requires in a first step a measurement of the chosen fundamental constant with contemporary lowest uncertainty and best reproducibility. The constant will then be fixed to that value. As an example the metre is related to the fixed constant speed of light.For the kg there are considered two ways: one is a watt balance, which determines the mass in units of the Planck constant, h. While at present the watt balances show a heterogeneous appearance, the second class of experiment the determination of the Avogadro constant, NA, which measures the mass in terms of the number of elementary entities has reached a considerable level of uncertainty and reproducibility. The fundament of the new determination of the Avogadro constant is a highly enriched 28Si crystal. The different working groups of the Avogadro team determine molar mass and lattice parameter of the crystal, and mass and volume of two precision spheres made from different positions, but of the same crystal. All measurements are carried out for both spheres and all measurement quantities are determined at least from two independent working groups, usually of different countries.

Mocvd of Polycrystalline and Epitaxial Complex Oxides by Liquid Delivery

1997 ◽  
Vol 474 ◽  
Author(s):  
J. F. Roeder ◽  
S. M. Bilodeau ◽  
R. J. Carl ◽  
T. H. Baum ◽  
P. C. Van Buskirk ◽  
...  
Keyword(s):  
Single Crystal ◽  
Current Density ◽  
Complex Oxides ◽  
The Other ◽  
Charge Storage ◽  
Growth Mechanisms ◽  
X Ray ◽  
Unique Approach ◽  
Bst Films ◽  
Liquid Delivery

ABSTRACTA unique approach to MOCVD of complex oxides enables deposition of a number of materials of technological importance through the use of liquid delivery of metalorganic precursors. Methodologies for control of composition and exploration of. process space are compared for two film systems, one in a relatively mature state of development ((Ba,Sr)Ti03), the other in an early state of development (Ni-ferrite). In both cases, composition was controlled by mixing metalorganic precursors dissolved in solvents using a liquid delivery system. Films with excellent crystalline quality were deposited in both cases. Polycrystalline BST films displayed properties suitable for DRAM applications: charge storage densities > 80 fF/μm2 and leakage current density < 10−8 A/cm2 for films as thin as 15 nm. Growth mechanisms and rates were determined for the single component oxides of the ferrite films. Epitaxial NiFe204 films were deposited on MgO single crystal substrates at 650°C; x-ray rocking curves yielded FWHM values of 0.046°, commensurate with the substrate.

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