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MS: Fachverband Massenspektrometrie

MS 9: Accelerator Mass Spectrometry and Applications II

MS 9.3: Vortrag

Donnerstag, 9. März 2017, 15:00–15:15, RW 2

Improvement of the Laser Ablation Interface for Direct ¹⁴C -AMS analysis of carbonates — •Christiane Yeman¹, Caroline Welte¹, Bodo Hattendorf², Joachim Koch², Marcus Christl¹, Lukas Wacker¹, and Allen Andrews³ — ¹Laboratory of Ion Beam Physics, ETH Zurich, 8093 Zurich, Switzerland — ²Laboratory for Inorganic Chemistry, ETH Zurich, 8093 Zurich, Switzerland — ³NOAA Fisheries, Pacific Islands Fisheries Science Center, HI 96818, USA

A novel method for direct and quasi continuous ¹⁴C analysis of carbonates was developed, where a laser ablation (LA) system is coupled to the gas ion source of the MICADAS (MIniCArbonDAtingSystem) accelerator mass spectrometer (AMS) at the Laboratory of Ion Beam Physics, ETH Zurich. By focusing a pulsed laser beam (ArF excimer laser 193 nm, 200 - 250 Hz) on the sample surface, CO₂ is produced, which is directly and continuously introduced into the gas ion source and analyzed for radiocarbon. With the new design of the ablation cell and the modified optical setup the energy on the sample is doubled leading to higher CO₂ production. Moreover, the spatial resolution has improved from 100µm down to 75µm.

LA-AMS can be used for the analysis of terrestrial and marine carbonate samples, such as stalagmites, corals, shells and otoliths. Here, we present the analysis of the otolith of a red snapper (Lutjanus campechanus) - only a few hundred micrometers thick - by LA-AMS. The ¹⁴C signature recorded for the lifespan of the fish shows pre-bomb and peak ¹⁴C, indicating the fish was more than 50 years old.