Isotope separation by nonlinear resonances in a Paul trap

Deviations from the ideal quadrupole potential in a Paul ion trap create nonlinear resonances at certain operating points inside the stability diagram, where in the absence of potential pertubations storing times 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 separate isotopes of a given element by choosing suitable trap operating conditions. Experiments on a natural mixture of Eu⁺ ions of mass 151 and 153 show that in a simple way, by proper choice of the operating point, the ions can be completely separated and laser-induced optical spectra 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 contrast to the usual way of using the mass dependent boundaries of the stability diagram