Studies On Spectra And Lifetime Of Highly Excited 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, the even-parity highly excited states of Europium (Eu) atom have been investigated by employing resonance excitation and electric field ionization (EFI) method. The Eu atom is first excited from the 4f 7 6s2 8^So_7/2 ground state to the 4f 7 6s7s (8^So_7/2 or 10So9/2) state via a 4f 7 6s6p ((10)^P9/2 or (10)^P7/2) state by the first two dye lasers. Then it is populated to many even-parity high-lying states in the energy region between 45525 cm-1 and 45707 cm-1 by scanning the wavelength of the third dye laser. Finally, the atom is detected by the electric field ionization (EFI) method. Eighty-nine states belonging to the 4f 7 6s(9^S)np (8PJ or (10)^PJ) Rydberg series are detected, whose principal quantum number and quantum defect are determined by analysing and comparing with literature. Besides, the present work reestimates the ionization limit of Eu atom at 45734.2 cm-1 and explains the existence of a broad profile below the ionization limit.Secondly, the lifetime of the 4f⁷6s(9^S)np bound Rydberg series of Eu atom are obtained with stepwise resonance excitation and detection method of electrical field ionization.Lastly, the autoionization spectra of the 4f⁷6s(7^S)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(7^S)np 6P5/2 and 6P7/2, converging to the second ionization limit 4f⁷6s 7^S4. 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 and lifetime 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.