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

Asymmetric satellites corresponding to interferences between 6p1/215d5/2 and 6p1/2nd5/2 states (n≠15) in the autoionization spectrum of Ba for the transition 6s15d¹D₂→6p1/2-15d5/2 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.