Studies On Spectra Of Bound And Autoionizing States Of Eu Atom

The investigations of highly excited states of the complex atom have important significance to science. It not only can unveil the atomic structures and their properties, but also can test the accuracy and validity of new theory of quantum mechanics. On the other hand, such studies may have great impacts and extensive applications on many high scientific and technical purposes, such as exploration of new mechanism of laser, and development of atomic energy. As a typical rare-earth atom, the Eu atom has a complex electronic configuration of [Xe]4f⁷6s², leading to rather complicated spectra with excitation of electrons in the half-filled 4f-shell. Since the study of the spectra of the Eu atom is very valuable and challenging, both bound and autoionizing states of Eu atom have been investigated systematically in this thesis.Firstly, both odd-parity and even-parity excited states of Eu atom are populated with stepwise resonance excitation, and detected with photoionization. The observables such as level energy and relative intensity are measured systematically. Furthermore, with the help of selection rules and comparison between the spectra obtained with different excitation paths, the total angular momenta are assigned to all the obtained states through a detailed analysis.Secondly, the spectra of the 4f⁷6s(⁹S)np bound Rydberg series of Eu atom are obtained with stepwise resonance excitation and detection method of electrical field ionization. Three Rydberg series, with J=5/2, 7/2 and 9/2, converging to the first ionization limit are identified. Many states of these series are determined with their level energies, principal quantum numbers and quantum defects.Lastly, the autoionization spectra of the 4f⁷6s(⁷S)np autoionizing Rydberg states of Eu atom are obtained with stepwise resonance excitation. With the information of their peak positions and relative intensities, these states can be classified into the two autoionization Rydberg series, 4f⁷6s(⁷S)np 6P5/2 and 6P7/2, converging to the second ionization limit 4f⁷6s 7S₄. Along with the experimental data of their positions, principal quantum numbers, quantum defects, and intensities, their line shapes are also discussed.Above all, in the present work, the spectra of highly excited states of Eu atom have been studied systematically with different excitation paths and detection methods. Not only many data of the Eu atom in literature are confirmed, but also lots of new data are measured. These achievements will greatly enrich the knowledge on the atomic spectroscopy of Eu atom, and provide valuable information for developing the new quantum theory on the complex atomic system.