INTERLOPER RESONANCES IN THE (3)SIGMA(-)(U) TRANSITORY STATES OF O-2

We have undertaken a detailed study of the various Rydberg resonance s eries found in the (3)Sigma(u)(-) symmetry for electron collisions wit h 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 detec ted, identified and analysed. An analysis of our results indicates the presence of 4p sigma(u), 5p sigma(u), 6p sigma(u), 3d pi(g) and 4f si gma(u) interloper resonances in the (3)Sigma(u)(-) scattering symmetry which have been assigned to the appropriate molecular oxygen cation t hreshold. The presence of these interlopers is seen to cause a perturb ation on the relevant spectral series disrupting the regular Rydberg s eries pattern. The results for several low-lying members of each Rydbe rg series are analysed in detail and compared with the available theor etical and experimental work.