Spectroscopic Properties of Perturbed Ba 6p_3/2ns Autoionizing States

The excitation spectra of the Ba 6p_3/2ns ( J = 1) autoionizing states with n ranging from 8 to 12 are measured using multistep laser excitation scheme. The measurements manifest that these states are strongly perturbed by the degenerate 6p_1/2nl states, as the resonance profiles are structured according to the corresponding perturbing states. The experimental data are well reproduced by multichannel-quantum-defect theory, with the parameters obtained from a previous R-matrix calculation.