Studies On Spectra Of Excited States Of The Sm 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 the development of novel laser and project of laser isotope separation. The Sm atom is a typical atom, whose spectra of excited states are most complex and worthful. In this thesis, both spectra of the odd-parity and even-parity of excited states of Sm atom are studied systematically. The experimental data are analyzed with theory of quantum mechnics.On the experimental side, we have measured many excited states with two different parities. For the states with odd-parity, the wavelength of the first laser is tuned to excite an Sm atom from the 4f66s2 7FJ(J=0-6) states to many atomic states with different electronic configurations, such as 4f66s6p and 4f55d6s2. The atoms in these excited states with odd-parity are then detected sensitively with photoionization using an ultraviolet laser with wavelength of 355nm. For the states with even-parity, an additional photon must be used. Namely, the atoms in the odd-parity states mentioned above are excited further by the second laser whose wavelength is scanned. These Sm atoms in in the high-lying even-parity states are probed by absorbing another photon from the second laser that plays a role of a two-step photoexcitation and photoionization. In another words, the innovation of this experiment is clearly demonstrated in combining different excitation schemes. Many measurements with different excitation schemes are carried out so as to obtain different sorts of information on the excited states of the Sm atom.On the theoretical side, we have performed an analysis on the spectral data using the concepts of quantum mechnics, such as spectral line intensity and selection rules of the dipole transitions on parity and different angular momenta. Based on the accuracy of wavelength calibration on the scanning lasers, we have identified many excited states of the Sm atoms according to their wavelengths of transitions. In some cases, we also have to calculate the relative intensities of spectral lines to determine the quantum numbers of the given states. Agreement between the theory and experiment is achieved in most cases.Above all, with a detailed analysis on the experimental data, we not only confirm some low-lying energy levels of the Sm atom reported in literature, but also report many new spectral data, which enrich the information of Sm atom significantly.