Interloper resonances in the transitory states of

We have undertaken a detailed study of the various Rydberg resonance series found in the symmetry for electron collisions with molecular oxygen ions. A five-state valence CI approximation is used in our expansion of the target molecular states within the ab initio close-coupling R -matrix approach to calculate the relevant eigenphase sum and associated cross sections. Rydberg resonances series are detected, identified and analysed. An analysis of our results indicates the presence of and interloper resonances in the scattering symmetry which have been assigned to the appropriate molecular oxygen cation threshold. The presence of these interlopers is seen to cause a perturbation on the relevant spectral series disrupting the regular Rydberg series pattern. The results for several low-lying members of each Rydberg series are analysed in detail and compared with the available theoretical and experimental work.