Role of Open Channels in Overlapping Resonances Studied by Multichannel Quantum Defect Theory in Systems Involving 2 Nondegenerate Closed and Many Open Channels

Previous work on the phase-shifted version of the multichannel quantum-defect theory (MQDT) for a system involving 2 closed and many open channels (Lee, C.-W. Bull. Korean Chem. Soc. 2010, 31, 1669) was extended to obtain the formulae of the spectral shape parameters with the structure of a pole extracted explicitly for general cases only limited by 2 non-degenerate closed channels. The theory was applied to the narrow $6p_{1/2,3/2}np$ J = 1 autoionizing Rydberg series in barium perturbed by the $6p_{3/2}nf$ states obtained by de Graaff et al.