Multistep laser excitation of barium: Apparent interferences due to overlap-integral variations

We report new, more extensive photoexcitation spectra of Ba autoionizing states which demonstrate that appearent interferences between discrete autoionizing states are in fact not interferences as previously proposed. A simple alternative interpretation of the "interference"-like line shapes as being due to variations in the spectral density of the autoionizing states and their overlap integrals with the bound initial state is presented and shown to agree with experiment. We argue that such spectra allow perhaps the most accurate determination of quantum defects, and should be a useful spectroscopic probe of autoionizing states.