Investigations of high-lying even-parity energy levels of atomic samarium using simultaneous observation of two-color laser-induced fluorescence and photoionization signals

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.…”