Polarized fluorescence spectroscopy of O2(+)

Polarized fluorescence measurements involving the A 2Pi(u) - X 2Pi(g) and b 4Sigma(g)(-) - a 4Pi(u) transitions in O2(+) following narrow-band photoexcitation of O2/X 3Sigma(g)(-)/ are reported. The analysis, based on the conventional high-J limit, involves deducing the quadrupole alignment factor from which the relative strengths of degenerate photoexcitation channels responsible for the population distribution in the A 2Pi(u) and b 4Sigma(g)(-) states of O2(+) can be estimated. The measured A-channel polarization exhibits pronounced structure which correlates well with the known positions of Rydberg states, whereas the polarization signal in the b channel has broad and less prominent features. Discrepancies between theoretical and measured results can largely be accounted for by additional configuration mixing and autoionization considerations.