Configuration interaction effects in the atomic photoelectron spectra of Ba, Sm, Eu, and Yb

High temperature photoelectron spectra of Ba, Sm, Eu, and Yb were studied using both He i and Ne i resonance lines. In addition to strong lines corresponding to transitions from the primary configurations, correlation satellites were observed in every spectrum. By comparing the spectra excited at different photon energies, the satellite lines found in all Ne i spectra and the He i spectrum of Yb were attributed to admixtures of the configurations 5d 2, 6p 2, etc., into the ground state. Autoionization is believed to occur at the energies of the He iα, He iβ, and Ne i satellite lines for Ba; at the He iα energy for Sm; and at the He iα and He iβ energies for Eu. Autoionization was detected by noting the dramatic increase in satellite intensities and, in some instances, the large deviation of the observed intensity ratios within multiplets from the statistical values. Photoelectron spectroscopy has been demonstrated to have great potential in providing detailed information about electron correlation in both initial and final states.