ISOTOPE-SEPARATION BY NONLINEAR RESONANCES IN A PAUL TRAP

Deviations from the ideal quadrupole potential in a Paul ion trap crea te nonlinear resonances at certain operating points inside the stabili ty diagram, where in the absence of potential pertubations storing tim es are very long. In the presence of those pertubations, however, the ions are lost from the trap. Since these resonances are mass dependent and the mass resolution is of the order of 100 it can be used to sepa rate isotopes of a given element by choosing suitable trap operating c onditions. Experiments on a natural mixture of Eu+ ions of mass 151 an d 153 show that in a simple way, by proper choice of the operating poi nt, the ions can be completely separated and laser-induced optical spe ctra of a single isotope can be received. This is the first time that mass separation in a Paul trap is performed by nonlinear effects in co ntrast to the usual way of using the mass dependent boundaries of the stability diagram