Accurate measurements of the autoionization widths of 5d5g levels of barium coupled to theoretical calculations, based on the eigenchannel R-matrix method and the multichannel quantum-defect theory, permit an investigation of the quadrupolar autoionization mechanism. The direct polarization of the inner electron by the outer one is an important correction to the Coulomb repulsion that causes autoionization. Also, the dielectronic polarization interaction significantly influences the autoionization widths. The occurrence of these polarization effects in the 5d5g doubly excited states with nonoverlapping valence electrons results in a significant narrowing of their widths and explains the failure of the ''single-configuration model'' for high-l Rydberg levels. © 1995 The American Physical Society.
|Physical Review A. Atomic, Molecular and Optical Physics
|Published - 1995