Study On 6pns Autoionizing States Of Ba Atom

The study on autoionizing states of two-electron atom is not only important for understanding the structures and properties of atom, but also helpful to the related scientific and technical fields, such as the development of novel laser and laser isotope separation etc. The Ba atom is a typical two-electron atom, whose autoionizing states still remain to be worthy of research. In the thesis, the topic is systematically and deeply studied for the further studies both experimentally and theoretically.On the experimental side, the experimental apparatus and approach are almost identical to those used previously, only a brief description is given here. The scheme of the three-step excitation of ICE is shown in the next text. The ICE technique is a special excitation method. For the Ba atom, the excitation procedure is: 6s~2→6s6p→6sns→6pns. Namely, three lasers excite the two valence electrons of the Ba atom with three transitions.On the theoretical side, the mutichannel quantum defect theory (MQDT) was used to analyze the experimental spectra. A 13-channel MQDT model was employed to reproduce the 6pns (J=1) autoioniziong states. Furthermore, the channel interactions in the auto ionization series were also analyzed in detail by calculating the corresponding channel mixing coefficients.Above all, three dye lasers are used to excite Ba atoms to obtain ions and electrons through autoionization process. The wavelength of the second laser is scanned when those of the first and third lasers are fixed, through which spectra of Ba 6sns Rydberg series are measured. The wavelength of the third laser is scanned when those of the first and second lasers are fixed, through which spectra of Ba 6pns autoionization series are measured. Experimental spectra are described and analyzed by multichannel quantum defect theory. The Ba Rydberg state and 6pns have been discussed in this paper. Agreement between the theory and experiment is achieved.