Observation of Interferences between Discrete Autoionizing States in the Photoexcitation Spectrum of Barium

Asymmetric satellites corresponding to interferences between $6p_{\frac{1}{2}}15d_{\frac{5}{2}}$ and $6p_{\frac{1}{2}}n{d}_{\frac{5}{2}}$ states ($n\ne 15$) in the autoionization spectrum of Ba for the transition $6s15d{}_{}{}^1{}_{}{}^{}D_2^{}{}_{}{}^{}\to 6p_{\frac{1}{2}}-15\mathrm{}{d}_{\frac{5}{2}}$ are observed. A simple line-shape theory based on first principles allows us to measure "two-electron" transition-matrix elements in terms of one-electron dipole-transition matrix elements. These values are compared to those calculated using a quantum-defect model which also explains the sign of the observed asymmetries.