title: (30)Si mole fraction of a silicon material highly enriched in (28)Si determined by instrumental neutron activation analysis.
abstract: The latest determination of the Avogadro constant, carried out by counting the atoms in a pure silicon crystal highly enriched in (28)Si, reached the target 2 × 10(-8) relative uncertainty required for the redefinition of the kilogram based on the Planck constant. The knowledge of the isotopic composition of the enriched silicon material is central; it is measured by isotope dilution mass spectrometry. In this work, an independent estimate of the (30)Si mole fraction was obtained by applying a relative measurement protocol based on Instrumental Neutron Activation Analysis. The amount of (30)Si isotope was determined by counting the 1266.1 keV γ-photons emitted during the radioactive decay of the radioisotope (31)Si produced via the neutron capture reaction (30)Si(n,γ)(31)Si. The x((30)Si) = 1.043(19) × 10(-6) mol mol(-1) is consistent with the value currently adopted by the International Avogadro Coordination.
authors.affiliation: †Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce 91, 10135 Torino, Italy.
authors.forename: Giancarlo
authors.initials: G
authors.lastname: D'Agostino
authors.affiliation: †Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce 91, 10135 Torino, Italy.|‡Department of Chemistry, University of Pavia, via Taramelli 12, 27100 Pavia, Italy.
authors.forename: Marco
authors.initials: M
authors.lastname: Di Luzio
authors.affiliation: †Istituto Nazionale di Ricerca Metrologica (INRIM), Strada delle Cacce 91, 10135 Torino, Italy.
authors.forename: Giovanni
authors.initials: G
authors.lastname: Mana
authors.affiliation: ‡Department of Chemistry, University of Pavia, via Taramelli 12, 27100 Pavia, Italy.
authors.forename: Massimo
authors.initials: M
authors.lastname: Oddone
authors.affiliation: §Physikalisch-Technische Bundesanstalt (PTB), Bundesallee 100, 38116 Braunschweig, Germany.
authors.forename: Axel
authors.initials: A
authors.lastname: Pramann
authors.affiliation: ∥Laboratorio Energia Nucleare Applicata (LENA), University of Pavia, via Aselli 41, 27100 Pavia, Italy.
authors.forename: Michele
authors.initials: M
authors.lastname: Prata