Relative formation probabilities for fluoride and oxyfluoride anions of U, Np,Pu and Am in accelerator mass spectrometry measurements at VERA

Fluoride molecular anions have emerged as a potential alternative to oxides for the analysis of actinides in AMS. Research at the Vienna Environmental Research Accelerator (VERA) has focused on mixing samples prepared in an Fe ₂O ₃ matrix with PbF ₂ for in situ fluoridation during the sputter process. The relative formation probabilities for a range of (oxy-)fluoride molecular anions of uranium, neptunium, plutonium, and americium have been found to be characteristic for each of the actinides investigated. These data can help to identify isobaric interference for the mentioned actinides. A first application is monitoring of the ²³⁶U co-production with ²³⁶Np during Th irradiation. Extracting these actinides in the form of tetrafluoride anions allows the suppression of U by an order of magnitude relative to Np.