Autoionization resonances in the Eu I absorption spectrum and a new determination of the ionization potential

Abstract

The absorption spectrum of europium has been studied at high resolution in the wavelength region between 2200 and 2100 Å. Two Rydberg series were found converging towards the 9 S 4 and 7 S 3 levels of the configuration 4f 7 6s in Eu II. The first series is perturbed near the series limit and the second shows strong autoionization features. A value of 45734.9 ± 0.2 cm -1 is deduced for the first ionization limit.

Field ionization process of Eu 4f76snp Rydberg states

“…[9,10] All rare-earth atoms, except for Yb, have a partially filled 4f subshell, resulting in the complicated spectra of highly excited states due to the very complex structures of the ground state. [11][12][13] In recent years, the spectral studies of highly excited states of the Eu atom, a typical complex rare-earth atom with electronic configuration of [Xe]4f 7 6s 2 , in zero field have been reported, [14,15] not only on bound states, [16,17] but also on some auto-ionizing states. [18,19] Due to the high selectivity and efficiency, the EFI method has been used for detection of highly excited states, [20,21] and determination of the first ionization limit [22] and the lifetimes of the Eu atom.…”