From oxide to fluoride: Optimizing measurement strategies for 99Tc by AMS and n-TIMS
Year: 2026
Type: article
Abstract: Quantifying the long-lived fission product 99 Tc ( 𝑡 1 / 2 = 2 . 1 1 1 × 1 0 5 yr) in environmental samples at global fallout levels (down to 1 0 6 atoms per L) remains challenging. Beyond suppressing the stable isobar 99 Ru, establishing a robust normalization method is a major challenge for mass spectrometric analysis of 99 Tc. We aim to benchmark two complementary approaches: in Accelerator Mass Spectrometry (AMS) we investigated non-isotopic normalization to the Nb-current extracted from the sample matrix in a Cs-sputter source, for extraction of the monoxide (TcO − ) and pentafluoride (TcF − 5 ) anions from the ion source at the Vienna Environmental Research Accelerator (VERA). The reproducibility of this non-isotopic normalization is sensitive to ion source operating conditions and ranges from 10%–30% (monoxide) and 20%–60% (pentafluoride). Ionization efficiencies of 99 TcO − and 99 TcF − 5 are reported for the first time as 0.4% and 0.03%, respectively. In parallel, we explored the feasibility of normalization using a 97 Tc spike in negative Thermal Ionization Mass Spectrometry (n-TIMS), for which the ionization efficiency of 99 TcO − 4 was determined to be 2%–10%. The suppression of 99 Ru and 97 Mo in n-TIMS was quantified for the first time, yielding upper-limit suppression factors of > 7 × 1 0 5 and > 5 × 1 0 4 relative to Tc, respectively.
Institutions: University of Vienna, Montanuniversität Leoben
Language: English
Subfield: Radiation
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $2,810
Funder: Universität Wien
OpenAlex ID: W7211991880