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Improved Uranium Particle Analysis by SIMS using O3- Primary Ions



Evan Groopman, Todd Williamson, David S. Simons


We have investigated the use of negative molecular oxygen primary ion beams (i.e., O2- and O3-) to determine the benefits of using such beams for uranium particle SIMS analyses. Typically, O- is the most practical negative primary ion species for both age dating and uranium isotopic analysis from the conventional duoplasmatron ion source. RF plasma ion sources make it possible to use O2- and O3- due to the increased abundance of molecular species in the plasma relative to the duoplasmatron. We have determined that by using an O3- beam, the ionization yield can be increased by a factor of approximately two over an O- beam, up to 4.7%, a substantial improvement which positively impacts measurement precision and detection limits. We also investigated the effect of the molecular oxygen beams on uranium isotope mass fractionation and the Th/U relative sensitivity factor for SIMS analyses in comparison to O- beams. We found that O3- reduced instrumental mass fractionation and matrix/substrate effects relative to the other negative ion beams. Particle measurements using O3- were improved in every respect compared to conventional O- beam analyses.
Journal of Analytical Atomic Spectrometry


SIMS, molecular oxygen, uranium particles, useful yield


Groopman, E. , Williamson, T. and Simons, D. (2022), Improved Uranium Particle Analysis by SIMS using O3- Primary Ions, Journal of Analytical Atomic Spectrometry, [online],, (Accessed April 17, 2024)
Created September 6, 2022, Updated November 29, 2022