Resonant oscillation modes of sympathetically cooled ions in a radio-frequency trap

The dynamics of sympathetically cooled ions, which were characterized by a resonant frequency in the time-averaged pseudopotential of the radio frequency trap, was studied. The ion trap consisted of one ring and two endcap electrodes of hyperboloid of revolution. It was found that the resonant frequency of the sympathetically cooled heavier ion species was larger than that of the pure ion without ²⁴Mg⁺ present. The observed results were explained by the theoretical model, in which the ion system was treated with the composition of a host ion cloud and a single guest ion, and interaction between them was taken into account.