Low-level detection of actinides by laser resonance photoionization

Laser resonance ionization mass spectrometry has been investigated as a method for the detection of trace amounts of actinides. High sensitivity and selectivity can be achieved by three-step photoionization followed by time-of-flight mass analysis. The laser system for photoionization consists of three dye lasers which are pumped simultaneously by a copper vapor laser. For mass determination a time-of-flight spectrometer with a mass resolution of about 1500 is used. By ionization via autoionizing states an overall efficiency of 4x10-6 was determined for 239Pu yielding a detection limit of less than 107 atoms. Isotope ratio measurements have been performed with synthetic plutonium samples. (orig.)