A new high precision determination of the atmospheric 21Ne abundance

Abstract

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 10¹² and 10¹³ ohm amplifiers, providing linearity and optimal dynamic range and signal/noise ratio. Following consideration of known possible sources of interference, and mass discrimination correction assuming an atmospheric ²²Ne/²⁰Ne ratio of 0.102, we derive the relative mass fractionation corrected ²¹Ne abundance in the terrestrial atmosphere, allowing us to determine a new ²¹Ne/²⁰Ne 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.