Isolated-core excitations in strong electric fields. III. The Ba 6p(j)nk series - art. no. 033408

The cross section for isolated-core excitation (ICE) of barium 6p(j)n'k' au toionizing states from 6snk Stark levels has been measured as a function of applied electric-field strength. For the most part, states that are well m ixed by the applied field have nearly Lorentzian line shapes indicating pre dominant ICE of a single autoionizing resonance with n'=n and k'=k. Small n on-lorentzian shake-up features in the wings of the lines are examined in d etail using high laser power to depletion broaden the main resonance and am plify the wings of the line shapes. While analogous shake-up features in ze ro-field ICE spectra are easily described theoretically, attempts to reprod uce the spectra observed in a field generally fail to provide good agreemen t. Finally, significant differences in excitation of Ba+ 6p(1/2) rather tha n Ba+ 6P(3/2) cores are observed.