Polarized fluorescence spectroscopy of O+2

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Abstract
Polarized fluorescence from the A 2Πu and b 4Σ−g states of O+2 following photoionization of O2(X 3Σ−g) in the 17–21 eV region has been employed to determine population alignment in the O+2 photoion. The measured A‐channel polarization exhibits pronounced structure which correlates well with the known positions of (autoionizing) Rydberg states, whereas polarization signal in the b channel has broad and less prominent features. The measured b‐channel polarization values (ranging from −0.02 to −0.05) are consistent with single‐channel calculations, while the A‐channel polarization measurements (which range from 0 to 0.09) are of opposite sign to the previously reported single‐channel calculations. The results of more involved calculations show that this sign reversal in the A channel can be attributed to the presence of intravalent 3Σ−u states which autoionize into the A channel in the near‐threshold region.