Measurements of Nitrogen in the Genesis concentrator target materials: sources of contamination N

Verchovsky, Sasha and Franchi, Ian (2010). Measurements of Nitrogen in the Genesis concentrator target materials: sources of contamination N. In: 41st Lunar and Planetary Science Conference, 1-5 Mar 2010, Houston, TX, US.

URL: http://www.lpi.usra.edu/meetings/lpsc2010/pdf/2127...

Abstract

Introduction: Measurement of N isotopic composition in the Genesis samples has turned out to be a tricky business. The results obtained so far in two laboratories are different by 700‰ (from -400 to +300‰)! The laboratories used different extraction methods and target materials: amalgamation of gold on sapphire and UV laser ablation of gold plated stainless steal. Both techniques are proven to be efficient enough and have been checked using artificially N-implanted target samples. However, the dramatic discrepancy between the obtained results clearly suggests that there is something wrong with one of the two, or perhaps both measurements. And though no obvious mistakes in the measurements have been found yet both of them suffered from some problems. In the case of amalgamation a potential problem is underestimation of the CO contribution at masses 28 and 29. In the case of laser extraction the main problem is with a high level (90% and more) of contamination of the gold layer with terrestrial N. Therefore, the solar wind (SW) δ15N value has been obtained in this case by a very long extrapolation. A more detailed look at the data obtained by has revealed some puzzling observations regarding the origin of the contamination N in the gold samples At the OU we have developed an alternative technique for analysis of SW N which utilises stepped oxidation of the Diamond-Like-Carbon (DLC) on Si (DoS) Genesis targets.

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