Investigation of the atomic structure of curium and determination of its first ionization potential

We report on the investigation of the atomic structure of curium ( Z=96 ) by resonance ionization spectroscopy. Three different excited energy levels were populated from the 5f^76d7s^2 ^9D^o_2 ground state as first excitation steps. Wide-range scans were performed for the search of second excitation steps around the literature value of the ionization potential. These spectra were analyzed to identify Rydberg levels and auto-ionizing resonances. The ionization potential was consistently determined as 48330.68(16) cm ^-1 through the evaluation of Rydberg convergences and the complementary approach of DC electric field ionization by evaluating the ionization threshold according to the saddle point model. The new result deviates by 6.7 cm ^-1 from the literature value of 48324(2) cm ^-1 by Köhler et al. [ 15 ] and is about one order of magnitude more precise. Graphic abstract