Resonance ionization mass-spectroscopy of neptunium

For the detection of trace amounts in ecological studies of 237Np, resonance ionization mass-spectroscopy has been explored. The experimental set-up consists of three tunable dye lasers pumped by two pulsed copper vapour lasers and a time-of-flight spectrometer. Several excitation schemes have been studied. For two schemes autoionizing levels could be observed. The hyperfine structure splitting of the resonance lines of the first and second excitation step have been investigated. The available laser powers were sufficient to saturate the first two excitation steps but not the ionization step. Without having optimum conditions, a detection limit of ≤ 1010 atoms could be reached. (Author)