Isolated-core excitations in strong electric fields. III. The Ba6pjnkseries

Abstract

The cross section for isolated-core excitation ͑ICE͒ of barium 6p j nЈkЈ autoionizing states from 6snk Stark levels has been measured as a function of applied electric-field strength. For the most part, states that are well mixed by the applied field have nearly Lorentzian line shapes indicating predominant ICE of a single autoionizing resonance with nЈϭn and kЈϭk. Small non-Lorentzian shake-up features in the wings of the lines are examined in detail using high laser power to depletion broaden the main resonance and amplify the wings of the line shapes. While analogous shake-up features in zero-field ICE spectra are easily described theoretically, attempts to reproduce the spectra observed in a field generally fail to provide good agreement. Finally, significant differences in excitation of Ba ϩ 6p 1/2 rather than Ba ϩ 6p 3/2 cores are observed.