Berlin 2001 – wissenschaftliches Programm
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MS: Massenspektrometrie
MS 3: Laser Resonance Ionization Mass Spectrometry
MS 3.2: Vortrag
Dienstag, 3. April 2001, 16:15–16:30, EB 202
41Ca Ultratrace-Determination by Diode-Laser-Based RIMS: Comparative Studies to AMS — •Christopher Geppert, Klaus Blaum, Jochen Maul, Peter Müller, Philipp Schumann, and Klaus Wendt — Institut für Physik, Johannes Gutenberg-Universität Mainz, D-55099 Mainz, Germany
We report on progress in development and application of 41Ca ultratrace determination by diode-laser-based RIMS. A number of applications require high selective ultratrace-determination of the long-lived isotope 41Ca. These include biomedical isotope-tracer studies, cosmochemical investigations, radiodating of geological and anthropological samples and environmental dosimetry. Depending on the application, 41Ca needs to be determined at isotopic abundance in the range of 10−9 to 10−15 relative to the dominant stable isotope 40Ca. Hence, isotopic selectivity of up to 1015, combined with overall detection efficiency of 10−6 to 10−4 is required. In our laser-mass-spectrometric approach we use an efficient atomization of the sample followed by triple-resonant optical excitation and subsequent nonresonant photoionization in a collimated atomic beam. All resonant steps are excited with extended cavity diode lasers. The resulting photo-ions are mass analyzed in a commercial quadrupole mass spectrometer, which provides additional suppression of neighboring masses by more than 106. With this method we demonstrated an overall efficiency above 5·10−5. The measured limit of detection in the relative isotope ratio of 41Ca/40Ca amounts to 3·10−13, limited dominantly by background effects. Measurements for environmental dosimetry, biomedical applications and Fe(p,x)41Ca-cross section determination are presented in comparison to corresponding AMS measurements.