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

The study on excited states of rare-earth atom is not only important for understanding the atomic structures and their properties, but also helpful to the related scientific and technical purposes, such as novel laser and laser isotope separation. However, the information about the highly excited states of the rare-earth atoms is still scanty. Especially, as a typical rare-earth atom, the spectra of the Eu atom excited states are most complex and abundant. So, the studying of the spectra of the Eu atom is very challenging and valuable. In this thesis, many spectra of the bound and autoionizing Rydberg states of Eu atom have been measured, from which a lot of experimental data are obtained with systematical analyses.Firstly, photoionization and autoionization detection method are used to study the spectra of the highly excited bound states of Eu atom. Different kinds of states in the same energy region are accessed and identified with different excitation schemes. The physical parameters such as level energy and relative line intensity are obtained through a detailed analysis.Furthermore, combination of the differences between excitation processes and the corresponding selection rules enables us to determine the total angular momenta of the states. Secondly, the autoionization spectra of atomic Eu, belonging to the 4f~76pnl (l=0, 2) configurations, have been systematically investigated using the three-step laser resonance ionization spectroscopy and the isolated-core-excitation(ICE) scheme. Not only the physical parameters, energy position and width of autoionizing states, are determined, but also the transition line-shape of them is concerned. All the experimental spectra of the autoionizing states are symmetric and confirmed to be the Lorentzian profiles, from which their peak positions and widths can be easily obtained from the fitting process.At last, we design an effective method to identify different types of highly excited states. The spectra of odd-parity states in the same region are detected with either photoionization or autoionization methods, from which we may separate the Rydberg states from the valence states. Furthermore, the effective quantum numbers of the Rydberg states are also discussed in detail with the quantum theory.In the experiment, the spectral information of highly excited states of Eu atom are obtained with high precision and reliability via the combination of wavelength calibration of tuning lasers and the error estimation on the experimental data, etc. With a systematic study on the spectroscopic properties and a detailed analysis on them we not only confirm some data of highly excited states of the Eu atom reported in literature, but also report many new spectral data. These results significantly enrich the spectroscopic information of Eu atom.