O01_02

Ion-Laser InterAction Mass Spectrometry for long-lived cosmogenic radionuclides in stony meteorites

Martschini M¹, Merchel S¹, Marchhart O¹, Wieser A¹, Golser R¹

¹University of Vienna - Faculty of Physics, Isotope Physics - VERA, Vienna, Austria

Accelerator mass spectrometry (AMS) is usually the method-of-choice for the detection of long-lived cosmogenic nuclides such as ¹⁰Be, ¹⁴C, ²⁶Al, ³⁶Cl, ⁴¹Ca, ⁵³Mn and 60Fe with half-lifes between 6 ka and 4 Ma. Until recently however, tedious radiochemical separation to deplete matrices and isobars was a prerequisite for AMS hindering fast analysis.

Now, the world-wide unique Ion-Laser InterAction Mass Spectrometry (ILIAMS) system developed at the Vienna Environmental Research Accelerator (VERA) [1] can eliminate the need for chemistry in selected cases, i.e. presently for samples with stable isotope abundance of ≥1‰ and isotopic ratios above 10^−11.

Laser photodetachment and ion-molecule-reactions of anions provide unprecedented isobar suppression for many AMS-isotopes by up to eleven orders of magnitude. Hence, ILIAMS-assisted AMS enables the direct detection of e.g., ²⁶Al/²⁷Al (~10⁻¹⁰, extraction of AlO⁻) and ⁴¹Ca/⁴⁰Ca (~10⁻¹¹, extraction of CaF3⁻) in simply-crushed stony meteorites containing intrinsic ~1% Al and Ca. The presence of isobars originating from the natively-abundant elements (15% Mg, 1‰ K) does not cause any analysis problem making radiochemical separation redundant.

This newly-established instrumental AMS (IAMS) is opening routes to high-sample throughput analysis, reasonable and fast provenance checks for (extra-)terrestrial origin and identification of frauds. Additionally, first ²⁶Al/²⁷Al (~10⁻¹¹) tests on terrestrial quartz samples from high altitudes used for exposure dating look promising to instantly set-up IAMS as a pre-screening and sample selection method for in-situ dating applications before starting tedious chemistry for more accurate results.

[1] M. Martschini et al. Radiocarbon 2021, first view, doi.org/10.1017/RDC.2021.73.