Study of the resonance structures of the interacting degenerate autoionizing Rydberg series perturbed by an interloper by multichannel quantum defect theory

A previous study by Lee et al (2011 J. Phys. B: At. Mol. Opt. Phys. 44 065002) on the resonance structures in autoionization Rydberg spectra, which are caused by two interacting autoionizing series perturbed by an interloper, is extended to the case of unequal coupling strengths. The method is applied to the Ba spectrum obtained by de Graaff et al (1990 Phys. Rev. A 42 5473-80). In this spectrum, the inter-series interaction term between two autoionizing Rydberg series perturbed by an interloper makes a negligible contribution to the spectral shape, even though its contribution to the cross section is found to be sizable. The peculiarity of the root structure of the line profile index for this spectra type could explain why q reversal frequently takes place around the resonance peak of an interloper and why the pattern of the satellite peaks leans towards the central peak.