Can a bound Rydberg level be pushed into its own continuum?

The authors consider the 4p photoelectron spectrum of xenon. This is a case for which a diagonalisation of the 4*4 matrix describing the interaction between the configurations 4p 5 4d 10 and 4p 6 4d 8 4f, using Hartree-Fock (HF) interaction integrals for the average energy of the configurations, gives energy levels with considerable 4p 6 4d 8 4f character above the 4p 6 4d 8 thresholds. This would suggest that, in cases of strong configuration interaction (CI), a discrete level can be pushed above the limit of the Rydberg series to which it belongs. The authors present a simple CI model which takes the difference in the degree of collapse of the 4f orbital between states into account. This model allows one to conclude that, if term dependence is included, no 4p 6 4d 8 4f level is pushed above the appropriate 4p 6 4d 8 threshold in Xe, and the authors conjecture that this result will hold in the general case. As input for the model they use solutions of multiconfiguration Hartree-Fock (MCHF) calculations for the terms of the two interacting configurations.