A new high precision determination of the atmospheric ~(21)Ne abundance

摘要

We have carried out a series of precise Ne-isotope measurements of atmospheric Ne-separates on a state-of-the-art high mass resolution Thermo-Fisher Helix MC Plus Noble Gas Mass Spectrometer. We used a combination of static and dynamic configurations and techniques that allow us to minimize possible analytical artifacts related to isobaric interferences, magnet hysteresis and detector efficiencies. All Ne-isotope signals were measured at high ion beam intensities on accurately intercalibrated Faraday collectors connected to 10(12) and 10(13) ohm amplifiers, providing linearity and optimal dynamic range and signaloise ratio. Following consideration of known possible sources of interference, and mass discrimination correction assuming an atmospheric Ne-22/Ne-20 ratio of 0.102, we derive the relative mass fractionation corrected Ne-21 abundance in the terrestrial atmosphere, allowing us to determine a new Ne-21/Ne-20 ratio of 0.0029577 +/- 14. This value is significantly more precise than any previously reported determinations, with implications for atmospheric models and standardization protocols, and potential improvements for the precision and accuracy of terrestrial cosmogenic neon exposure dating, in particular for young exposure ages.