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MS: Fachverband Massenspektrometrie
MS 4: Accelerator Mass Spectrometry
MS 4.3: Talk
Wednesday, March 16, 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 (T1/2=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.