A determination of the Avogadro Constant

Sevfried, P.; Becker, Peter; Kozdon, Andrzej F.; Lüdicke, Fabian; Spieweck, F.; Stümpel, J.; Wagenbreth, H.; Windisch, D.; Bièvre, Paul De; Ku, H. H.; Lenaers, G.; Murphy, Thomas J.; Peiser, H. S.; Valkiers, S.

doi:10.1007/bf01309282

Cited by 99 publications

(47 citation statements)

References 18 publications

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“…These measurements give a value of N A of 6.022 0943 × 10 23 mol -1 , with an uncertainty of 1.05 × 10 -6 × N A . This appeared to represent a 30-fold reduction in the uncertainty from previous direct measurements [99], but, owing to an unsuspected error in measurement, had to be corrected later by more than the originally estimated uncertainty [52,106].…”

Section: Atomic Weights For Fundamental Constantsmentioning

confidence: 99%

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Laeter¹,

Böhlke²,

Bièvre³

et al. 2003

Pure and Applied Chemistry

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906

554

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Republication or reproduction of this report or its storage and/or dissemination by electronic means is permitted without the need for formal IUPAC permission on condition that an acknowledgmentAbstract: A consistent set of internationally accepted atomic weights has long been an essential aim of the scientific community because of the relevance of these values to science and technology, as well as to trade and commerce subject to ethical, legal, and international standards. The standard atomic weights of the elements are regularly evaluated, recommended, and published in updated tables by the Commission on Atomic Weights and Isotopic Abundances (CAWIA) of the International Union of Pure and Applied Chemistry (IUPAC). These values are invariably associated with carefully evaluated uncertainties. Atomic weights were originally determined by mass ratio measurements coupled with an understanding of chemical stoichiometry, but are now based almost exclusively on knowledge of the isotopic composition (derived from isotope-abundance ratio measurements) and the atomic masses of the isotopes of the elements. Atomic weights and atomic masses are now scaled to a numerical value of exactly 12 for the mass of the carbon isotope of mass number 12. Technological advances in mass spectrometry and nuclear-reaction energies have enabled atomic masses to be determined with a relative uncertainty of better than 1 × 10 -7 . Isotope abundances for an increasing number of elements can be measured to better than 1 × 10 -3 . The excellent precision of such measurements led to the discovery that many elements, in different specimens, display significant variations in their isotope-abundance ratios, caused by a variety of natural and industrial physicochemical processes. While such variations increasingly place a constraint on the uncertainties with which some standard atomic weights can be stated, they provide numerous opportunities for investigating a range of important phenomena in physical, chemical, cosmological, biological, and industrial processes. This review reflects the current and increasing interest of science in the measured differences between source-specific and even sample-specific atomic weights. These relative comparisons can often be made with a smaller uncertainty than is achieved in the best calibrated "absolute" (= SI-traceable) atomic-weight determinations. Accurate determinations of the atomic weights of certain elements also influence the values of fundamental constants such as the Avogadro, Faraday, and universal gas constants. This review is in two parts: the first summarizes the development of the science of atomic-weight determinations during the 20 th century; the second summarizes the changes and variations that have been recognized in the values and uncertainties of atomic weights, on an element-by-element basis, in the latter part of the 20 th century.J. R. de LAETER et al.

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Section: Atomic Weights For Fundamental Constantsmentioning

confidence: 99%

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Laeter¹,

Böhlke²,

Bièvre³

et al. 2003

Pure and Applied Chemistry

Self Cite

906

554

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“…Some further refinement of the gas mass-spectrometric measurement has been achieved. In that method SiFj* ions generated from a synthetic mixture of highly enriched specimens of Si isotopes are compared with these ions from the RMs of proven internal homogeneity [4]. Improved data analysis has in the meantime also been developed and adopted for all "standard atomic weight" evaluations by the Commission on Atomic Weights and Isotopic Abundances of the ' Formerly: Central Bureau for Nuclear Measurements.…”

mentioning

confidence: 99%

Letter to the Editor: New values for silicon reference materials, certified for isotope abundance ratios

Bièvre¹,

Valkiers²,

Peiser³

1994

J. RES. NATL. INST. STAN.

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New isotope abundance and relative atomic mass (atomic weight) values — with low, hitherto unattained uncertainty — are reported for two previously described silicon reference materials using a well-known method with an improved isotope-ratio mass spectrometer. These new values are directly traceable to the SI, more specifically to the unit for amount of substance, the mole, and independent of the SI unit of mass and of the Avogadro constant. Besides the residual mass-spectrometric uncertainties, these new values depend in effect only on a recently published direct comparison of the cyclotron frequency in a Penning trap of 28 Si + with that of 12 C + .

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“…Once the temperature is known with a precision of 0.1 K, the diffracted wavelength can be easily determined with good accuracy from the small angular separation between the two near-back-diffraction peaks, using the precisely measured lattice parameter of silicon (Seyfried et al, 1992).…”

Section: Resultsmentioning

confidence: 99%

X-ray Back-Diffraction Profiles with an Si (111) Plate

Cusatis¹,

Udron²,

Mazzaro³

et al. 1996

Acta Cryst Sect A

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A two-and, alternatively, a four-crystal monochromator were used for simultaneous measurements of the profiles backward (h) and forward (o) diffracted by a thin Si (111) crystal plate for diffraction angles up to exactly 90 ° at DCI-LURE (Orsay). It is shown that the set-up with a four-crystal monochromator allows the characterization of the back-diffraction region for any crystal plate reflection. Asymmetry and full width at half-maximum (FWHM) of the experimental backwarddiffraction profiles are analyzed. Possible simultaneous diffractions occurring near 90 ° incidence, giving extra peaks in the forward-diffracted profiles, are studied. The good contrast of the o-beam profiles suggests that the back-diffracted o beam could be used as a highly monochromatic beam.

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A determination of the Avogadro Constant

Cited by 99 publications

References 18 publications

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Atomic weights of the elements. Review 2000 (IUPAC Technical Report)

Letter to the Editor: New values for silicon reference materials, certified for isotope abundance ratios

X-ray Back-Diffraction Profiles with an Si (111) Plate

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