Studies On Spectra And Properties Of The Highly Excited States Of The Sm Atom

The investigation of highly excited states of the rare-earth atom is not only an important subject in the atomic physics, astrophysics and plasmas, but also helpful for the related scientific and technical fields, such as laser isotope separate, development of new laser and lasing without population inversion etc. The Sm atom is a typical rare-earth atom, with an open 4f shell, the spectra of highly excited states are most complex. In this thesis, both spectra and properties of the highly excited states of the Sm atom are investigated systematically and deeply.For bound states, three-step autoionization detection method and direct photoionization detection method are employed. When autoionization detection method is used, the wavelength of the first laser is fixed at 4f 66s2→4f 66s6p resonant transition and the wavelength of the third laser is fixed in the vicinity of 4f 66s+→4f 66p+ or 4f 66s+→4f 55d6s+ resonant transition, while the wavelength of the second laser is scanned between 400nm and 700nm. When direct photoionization detection method is used, the wavelength of the first laser is fixed at 4f 66s2→4f 66s6p resonant transition, and the wavelength of the second laser is scanned to excited the atoms to highly excited states, then these states are ionized by absorbing another photon from the second laser. Comparisons between the results from the two detection methods enable us to identify the Rydberg states from the valence states in the same energy energy with the information of level energies and their relative intensities and total angular momenta.The autoionizing states of the Sm atom, belong to 4f 66pnl and 4f 55d6snl (l=0, 2) configurations, are investigated by using a three-step isolated-core-excitation (ICE) scheme. These states are obtained by scanning the wavelength of the third laser across the 4f 66s+→4f 66p+ or 4f 66s+→4f 55d6s+ resonant transition while the wavelengths of the first two lasers are fixed, and they can be classified into different autoionization series in the light of the different ionization limits. In most cases, the transition profiles of these autoionizing states are nearly symmetric, from which the level energies and widths can be obtained easily by fitting the experimental spectra to the Lorentzian profiles. In addition, the spectroscopic properties of these autoionizing states are also discussed.Above all, the spectra of the highly excited states are investigated and many new states are reported. This work not only greatly enriches the spectral information of the Sm atom but also confirms the ICE scheme is still validity for the Sm atom. This study on highly excited states of the Sm atom is expected to stimulate more experimental and theoretical work in the further.