Ca-41 ultratrace determination with isotopic selectivity > 10(12) by diode-laser-based RIMS

Ca-41 ultratrace determination by diode-laser-based resonance ionization ma ss spectrometry with extremely high isotopic selectivity is presented. Appl ication to environmental dosimetry of nuclear reactor components, to cosmoc hemical investigations of production cross sections, and biomedical isotope -tracer studies of human calcium kinetics are discussed. Future investigati ons are possible use in Ca-41-radiodating. Depending on the application, Ca -41 isotopic abundances in the range of 10(-9) to 10(-15) relative to the d ominant stable isotope Ca-40 must be determined. Either double- or triple-r esonance optical excitation with narrow-band extended cavity diode lasers a nd subsequent non-resonant photoionization of calcium in a collimated atomi c beam were used. The resulting photoions are detected with a quadrupole ma ss spectrometer optimized for background reduction and neighboring mass sup pression. Applying the full triple-resonance scheme provides a selectivity of similar to 5 x 10(12) in the suppression of neighboring isotopes and > 1 0(8) for isobars, together with an overall detection efficiency of similar to 5 x 10(-5). Measurements on a variety of sample types are discussed; the accuracy and reproducibility of the resulting Ca-41/Ca-40 isotope ratios w as better than 5%.