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MS: Massenspektrometrie

MS 4: Resonanzionisations-Massenspektrometrie

MS 4.1: Vortrag

Donnerstag, 7. März 2002, 14:00–14:15, HS 02/E04

Atom Trap Trace Analysis of ⁴¹Ca — •Steven Hoekstra, Carolijn van Ditzhuijzen, Ronnie Hoekstra, Hans Wilschut, and Reinhard Morgenstern — KVI Atomic Physics, Rijksuniversiteit Groningen, Zernikelaan 25, 9747 AA, Groningen, The Netherlands

We are developing a new apparatus for ultra-sensitive trace analysis. Using modern optical methods to manipulate atoms, specific isotopes of calcium will be selectively cooled, trapped and detected in a Magneto-Optical Trap (MOT). Of special interest is the radioactive isotope ⁴¹Ca, which can be used for dating calcium-containing material from the pleistocene (the half-life of ⁴¹Ca is 10⁵ year) and for biomedical tracer studies of osteoporosis. The main experimental challenge is the very low natural abundance relative to ⁴⁰Ca, which is only 10⁻¹⁵ to 10⁻¹⁴. Until now this kind of experiments were attempted with Accelerator Mass Spectrometry (AMS). A combination of some recently developed techniques in the field of laser manipulation of neutral atoms enables us to build a table-top size, cost-effective alternative. The calcium atoms are evaporated in an oven, after which the atomic beam is decelerated in a Zeeman slower. Before and after the Zeeman slower the ⁴¹Ca atoms are selectively focused by a magneto-optical lens. After the Zeeman slower only the desired isotope is deflected by means of optical molasses into the central vacuum chamber, where six laserbeams together with the anti-Helmholtz coils form a traditional MOT. There the atoms are trapped, and detected by their fluorescence. Recently it has been shown that single atom counting in a MOT is possible.