Comparison of the INRIM and PTB lattice-spacing standards

To base the kilogram definition on the atomic mass of the silicon 28 atom, the present relative uncertainty of the silicon 28 lattice parameter must lowered to 3E-9. To achieve this goal, a new experimental apparatus capable of a centimetre measurement-baseline has been made at the INRIM. The comparison between the determinations of the lattice parameter of crystals MO*4 of INRIM and WASO4.2a of PTB is intended to verify the measurement capabilities and to assess the limits of this experiment.Comment: 10 pages, 8 figures, submitted to Metrologi

measurement of the lattice parameter of a silicon crystal

The silicon crystal WASO04 is a reference in the adjustment of fundamental physical constants, but its lattice parameter has never been measured in absolute terms. In the framework of an international project meant to base the kilogram definition on the molar volume and the lattice parameter of 28Si, the WASO04 crystal has been used to manufacture an interferometer prototype for the performance testing and the fine-tuning of a new experimental apparatus for lattice parameter measurements by combined x-ray and optical interferometry. The present paper discusses the test results and gives an accurate lattice parameter determination. With respect to previous determinations, the value obtained, d220(WASO04)=192.015 570 2(10) pm, displays a four-fold improvement in accurracy

An accurate 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, 6.02214084(18) x 10^23 mol^-1, is the most accurate input datum for a new definition of the kilogram.Comment: 4 pages, 5 figures, 3 table

Improved measurement results for the Avogadro constant using a 28Si-enriched crystal

New results are reported from an ongoing international research effort to accurately determine the Avogadro constant by counting the atoms in an isotopically enriched silicon crystal. The surfaces of two 28Si-enriched spheres were decontaminated and reworked in order to produce an outer surface without metal contamination and improved sphericity. New measurements were then made on these two reconditioned spheres using improved methods and apparatuses. When combined with other recently refined parameter measurements, the Avogadro constant derived from these new results has a value of $N_A = 6.022 140 76(12) \times 10^{23}$ mol$^{-1}$. The X-ray crystal density method has thus achieved the target relative standard uncertainty of $2.0 \times 10^{-8}$ necessary for the realization of the definition of the new kilogram.Comment: postprint, 22 page, 3 figures, 14 table

Systematische Untersuchung der K-Schalen-Absorptionsspektren der kubisch und pyramidal koordinierten Elemente Titan und Vanadium in komplexen Molekuelen und Festkoerpern

SIGLEAvailable from TIB Hannover: RN 4852(90-43) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

DOUBLE EXCITATION IN THE K - SHELL ABSORPTION SPECTRUM OF SULPHUR IN H2S AND D2S

The X- ray absorption spectra of H2S and D2S were studied near the sulphur K - edge at high resolution using synchrotron radiation as a continuous background source. In addition to the well-known single electron excitation lines ws observe two new structures in the continuum. On the basis of single configuration Hartree - Fock calculations we assign these features to two-electron transitions leading to levels of the final state configurations 1s2s2p63s2p34s np,ns, 4p np and 3d np and to excited states of the ion 1s2s2p63s2p3 ns, np, nd εp