Investigations On Ba 6pnd(J=1,3) Autoionizing States

Ba 6p1/2nd (J=1,3) and 6p3/2nd (J=1,3) autoionizing states, especially those with lower principal quantum number, have been systematically studied, using the isolated core excitation scheme with three dye lasers. Experimental spectras of Ba 6p1/2,3/2nd(J=1,3) autoionizing states, which are excited from 6snd1D2 Rydberg states with n=7-15 and from 6snd3D2 Rydberg states with n=7-12, are shown for the first time. The datas of energy level positions and widths have been measured, by fitting the spectra to the Lorentzian profile. An analysis with the multichannel quantum defect theory (MQDT) is carried out to explain the complex spectral structures in the observed spectra. Moreover, comparisons between the autoionization series converging to 6p1/2~+ and 6p3/2~+ are made. Furthermore, The MQDT model, as a powerful theoretical method, is examined on the ultimate case with the lowest quantum number n=7, where the correlation effect between the Rydberg and core electrons becomes much stronger.Experimental and theoretical studies of 6p1/2nd (J=1,3) and 6p3/2nd (J=1,3) autoionizing states closing to 6p1/2~+ ionization threshold have been carried out, which enrich the information of atomic spectra. Spectra of autoionizing states with the lowest principal quantum number exhibit much admixture between the two series converging to the 6p1/2~+ and 6p3/2~+ ionization thresholds. Further study of this channel-admixture effect is carried out with fitting of Lorentzian line-shape and MQDT method.On the other hand, autoionzation detection, as one of the newly developed techniques of highly sensitive detection, is used in this work, which avoids the shortcomings of field ionization and direct photon ionization. Some autoionizing states can not be seen, such as 6p1/2,3/210d, and these phenomena, which in turn can be used as a handy method for the purpose of laser frequency calibration, have been systematically discussed.