Ion trap nuclear resonance on ¹⁵¹Eu⁺

Laser-microwave double resonance techniques applied to a cloud of a natural mixture of Eu⁺ isotopes confined in a Penning trap has been used to induce and detect nuclear Zeeman transitions. In spite of the complex level structure of Eu^- and overlapping spectra from the two isotopes five different δm_I = 1 transitions could be observed from which the nuclear magnetic moment can be derived. We obtain for ¹⁵¹;Eu⁺ g_I = 1.377 34(6) demonstrating the potential for high accuracy of the technique. The experiment can be considered as a feasibility test that precise spectroscopy data using the ion storage technique can be obtained of very complex ions and under unfavourable conditions.