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arXiv · 1010.3088

Measurement of the \{220\} lattice-plane spacing of a $^{28}$Si crystal

Enrico Massa·Giovanni Mana·Ulrich Kuetgens·Luca Ferroglio
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Abstract

The spacing of the \{220\} lattice planes of a $^{28}$Si crystal was measured by combined x-ray and optical interferometry to a $3.5\times 10^{-9}$ relative accuracy. The result is $d_{220}=(192014712.67 \pm 0.67)$ am, at 20.0 $^\circ$C and 0 Pa. This value is greater by $(1.9464 \pm 0.0067)\times 10^{-9} d_{220}$ than the spacing in natural Si, a difference which confirms quantum mechanics calculations. Subsequently, this crystal has been used to determine the Avogadro constant by counting the Si atoms, a key step towards a realization of the mass unit based on a conventional value of the Planck or the Avogadro constants.

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Enrico Massa, Giovanni Mana, Ulrich Kuetgens, Luca Ferroglio. 2010-10-15. Measurement of the \{220\} lattice-plane spacing of a $^{28}$Si crystal. https://doi.org/10.1088/0026-1394/48/2/s06

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