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MS: Fachverband Massenspektrometrie

MS 4: Accelerator Mass Spectrometry

MS 4.3: Vortrag

Mittwoch, 16. März 2022, 11:15–11:30, MS-H9

Separation of U and Np Isobars by ILIAMS — •Andreas Wiederin¹, Karin Hain¹, Martin Martschini¹, Aya Sakaguchi², Peter Steier¹, and Robin Golser¹ — ¹University of Vienna, Faculty of Physics - Isotope Physics, Austria — ²University of Tsukuba, Faculty of Pure and Applied Science, Japan

²³⁷Np (T_1/2=2.1 Ma) is the second most abundant anthropogenic actinide in the environment, but a reliable quantification by AMS independent of the environmental matrix would require an isotopic spike for normalization. We currently consider ²³⁶Np the most suitable candidate to serve this purpose. Such a spike material is currently under development and needs a careful characterization regarding interfering by-products. Possible isobaric background from ²³⁶U necessitates the separation of U and Np by chemical means and/or during the AMS measurement. Ion Laser InterAction Mass Spectrometry (ILIAMS) uses selective laser photodetachment inside an RFQ ion cooler to neutralize anions of the interfering isobar. By applying a 2.33 eV laser, UF₄⁻ has been suppressed by at least four orders of magnitude in recent experiments, while NpF₄⁻ passed unaffected. The comparatively low formation rate and high sensitivity to interactions with the buffer gas of UF₄⁻ further increased the suppression relative to NpF₄⁻. This result represents the first isobar separation in the mass range of the actinides in AMS. The U suppression achieved is already sufficient for the application of ²³⁶Np to quantitatively determine ²³⁷Np by isotope ratio measurements.