237 Np Mössbauer isomer shifts in neptunium chalcogenides

Abstract

We report237Np Mossbauer spectrometry measurements on some Np polychalcogenides: NpS3,β-NpS2, Np3Se5, NpTe3,α-Np2S3 andγ-Np2Se3. The experiments have been performed at 4.2 K and 77 K. From the isomeric shift values, the oxidation state of the Np ion can easily be assigned in these kinds of compounds: Np(IV) in NpS3,β-NpS2 and Np(III) in NpTe3,α-Np2S3 andγ-Np2 Se3. A mixture of Np(III) and Np(IV) ions has been observed in Np3Se5. Comparisons of theIS values have pointed out the influence of the electronegativity of the chalcogen atom and of the bond length Np-X(X≡ S, Se, Te).