Use of surface ionization for rapid separation of isobar nuclides of La, Ce, and Pr

Abstract

Element-specific properties of a surface ion source are used for the rapid Z-separation of isobar nuclides of rare earths. The ionic yields and the separation efficiencies are determined by differences in the ionization potentials and the desorption energies (mean residence times). Consequently, during a temperature flash of the ionizing tungsten ribbon, adatoms of different rare earth elements desorb partially ionized at different times (different temperatures). An oxygen coverage of the surface may influence the ionization and desorption processes, and thereby the success of this method, very strongly. With La and the rare earth elements Ce and Pr it even plays a dominant role, since effective oxide formation occurs on the surface. Differences in the temperature dependence of the oxidation rates now provide an additional separation effect, if the mass spectrometer is tuned to the mass number of the corresponding oxide. By evaporating rare earth chlorides onto the tungsten ribbon, exposed simultaneously to oxygen, we performed flash-filament simulation experiments with different heating rates between 20 K/s and 7000 K/s.