Düsseldorf 2007 – wissenschaftliches Programm
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MS: Fachverband Massenspektrometrie
MS 4: Neue Trends und Anwendungen in der AMS
MS 4.7: Vortrag
Dienstag, 20. März 2007, 18:00–18:15, 5F
Electron Affinity Measurements on Fluorides of Hf and W — •Christoph Diehl1, Anton Lindahl2, Pontus Andersson2, Oliver Forstner3, Robin Golser3, Dag Hanstorp2, Fabio Schwellnus1, and Klaus Wendt1 — 1Institut für Physik, Johannes Gutenberg Universität Mainz, D-55099 Mainz — 2Department of Physics, Göteborg University, SE-412 96 Göteborg — 3Institut für Isotopenforschung und Kernphysik, VERA-Laboratorium, Universität Wien, Währinger Strasse 17, A-1090 Wien
182Hf is an ultratrace isotope with a half-life of 9 million years, which is produced e.g. in supernovae. Determination of the abundance of 182Hf in geological samples gives insight into the history of nearby supernovae events within the last ≈ 30 million years. At the VERA AMS facility in Vienna first studies on this topic were carried out and upper limits for the ratio 182Hf/180Hf in deep sea sediments were reported [1]. For further studies it is necessary to improve isobaric selectivity of the tandem accelerator AMS system used. As Hf negative ions are instable, AMS utilizes HfFx molecules and a significant background of WFx has to be suppressed. Laser photodetachment of WFx−, leaving the HfFx−, unaffected seems to be a promising possibility for that step. For preparation investigations of the so far unknown electron affinities of the fluorides of Hf and W are under way at the Göteborg University Negative Ion Beam apparatus. Collinear laser ion beam photodetachment is used to determine the photodetachment threshold. First results and future improvements of the apparatus are discussed.
[1] Vockenhuber et al., New Astr. Rev. 48, I 1-4, 161 (2004)