41Ca ultratrace determination with isotopic selectivity > 1012 by diode-laser-based RIMS

41Ca ultratrace determination by diode-laser-based resonance ionization mass spectrometry with extremely high isotopic selectivity is presented. Application to environmental dosimetry of nuclear reactor components, to cosmochemical investigations of production cross sections, and biomedical isotope-tracer studies of human calcium kinetics are discussed. Future investigations are possible use in 41Ca-radiodating. Depending on the application, 41Ca isotopic abundances in the range of 10–9 to 10–15 relative to the dominant stable isotope 40Ca must be determined. Either double- or triple-resonance optical excitation with narrow-band extended cavity diode lasers and subsequent non-resonant photoionization of calcium in a collimated atomic beam were used. The resulting photoions are detected with a quadrupole mass spectrometer optimized for background reduction and neighboring mass suppression. Applying the full triple-resonance scheme provides a selectivity of ∼ 5 × 1012 in the suppression of neighboring isotopes and > 108 for isobars, together with an overall detection efficiency of ∼ 5 × 10–5. Measurements on a variety of sample types are discussed; the accuracy and reproducibility of the resulting 41Ca/40Ca isotope ratios was better than 5%.