Spectra And Properties Of Bound And Autoionizing States Of Sm Atom

Study on the highly excited states is not only important for the development of atomic physics but also valuable for many applications, such as new laser, laser isotope separation. Sm atom is a typical rare-earth atom which not only has seven ground terms, but also has 6s 2 shell and unstable 4f⁶ shell. The complicated electronic structure makes its spectra very complex. Currently, study on its spectral properties is not only lack of effective theory, but also pose challenge on experimental method. In this thesis, both spectra and properties of bound states and autoionizing state of Sm atom have been studied systematically.According to selection rules of dipole transition many highly excited states have been detected with different excitation paths in the same energy region. Based on precise calibration of wavelength, the level energies of all states have been determined. A unique total angular momentum has been assigned to many states by comparing the spectra obtained with different excitation paths. In addition the relative line intensities of all transitions have been normalized to one, and the letters w, m and s have been used to represent the intensities.Spectra of bound highly excited states of the Sm atom, including even-parity states in 30040—38065 cm^-1 energy region and odd-parity states in 44111.7—45490.6 cm^-1 energy region, have been studied with stepwise excitation and photoionization detection method. For even-parity states, the first laser with a fixed wavelengthλ₁ excites the Sm atom from the initial state 4f⁶6s²⁷F_J (J=0-6) to the intermediate state 4f66s6p, from which the second laser, with a scanned wavelengthλ₂, excites it further to the even-parity states where it is detected by photoionization. For odd-parity states, the first laser with a fixedλ₁ excites the Sm atom from the initial state 4f⁶6s²⁷F_J (J=0-6) to the first intermediate state 4f⁶6s6p, from which the second laser, with a fixedλ₂, excites it futher to the second intermediate state 4f66s7s, then the wavelength of the third laserλ₃ is scanned in a certain energy region, the atom is resonantly excited to given odd-parity states where it is detected by photoionization.Spectra of autoionizing states of the Sm atom in 45948.9—46943.6 cm^-1 energy region have been investigated by three color multi-step resonant excition scheme with three different excitation paths. The Sm atom from the initial state 4f⁶6s2 7F_J (J=0-6) is excited to the intermediate state 4f⁶6s7s by the two laser with a fixedλ₁ andλ₂, then the Sm atom is excited to the autoionizing states by scanning theλ₃, where the Sm atom may automatically decay into an ion and an electron, thus achieve the detection of the autoionizing states.Based on the detailed analysis of the spectra, the level energies of these highly excited states and their relative line intensities have been determined with assignment of the J. The line widths and the forming mechanism of the line shape of autoionizing states have also been discussed. Most mentioned above has not been reported previously which not only enriches the information of Sm atom, but also provides foundation to many related fields.