Erlangen 2022 – wissenschaftliches Programm

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MS: Fachverband Massenspektrometrie

MS 2: Mass Spectrometry Methods

MS 2.1: Hauptvortrag

Montag, 14. März 2022, 16:30–17:00, MS-H9

Ion Laser InterAction Mass Spectrometry with fluoride molecular anions — •Martin Martschini¹, Karin Hain¹, Maki Honda^1,3, Johannes Lachner², Oscar Marchhart¹, Silke Merchel¹, Carlos Vivo-Vilches², and Robin Golser¹ — ¹University of Vienna, Faculty of Physics, Austria — ²HZDR, Dresden, Germany — ³NSRC, JAEA, Japan

AMS generally has the best abundance sensitivity for long-lived radionuclides, but the detection of ⁴¹Ca, ⁹⁰Sr, ⁹⁹Tc, ¹³⁵Cs and ¹⁸²Hf in the general environment has been limited or even hampered by strong isobaric interferences. Using molecular fluoride anions, the novel technique of Ion Laser-InterAction Mass Spectrometry (ILIAMS) provides unprecedented isobar suppression for these nuclides of 10⁴-10⁸ inside an RFQ ion guide. Therein, isobaric molecules are efficiently eliminated via laser photodetachment. In addition, molecular interactions with the buffer gas further enhance isobar suppression, e.g. via breakup of KF₃⁻ into KF₂⁻ + F or via O-pickup of WF₅⁻. Thereby, the VERA-facility has recently achieved the most sensitive detection of ¹⁸²Hf and ⁹⁰Sr, the latter at the 15 attogram level. For ⁴¹Ca, the blank level with CaF₃⁻ and ILIAMS is ⁴¹Ca/⁴⁰Ca = (1.5_−1.5^+1.7)×10⁻¹⁵. Recent tests also demonstrated that ⁴¹Ca can now be measured directly in stony meteorites with sample sizes down to 1-2 mg without performing any chemical preparation, i.e. in the presence of ∼1000 ppm K. This talk will review these benefits of fluoride anions with ILIAMS but also discuss the challenges involved like the strong parasitic ion current and the influence of excited molecules coming from a sputter ion source.