Comparison of theoretical and experimental (in absolute and relative measurement) (McLaughlin et al. 2014) single PI cross sections of O³⁺. Theoretical cross sections have been convolved with a Gaussian profile of 170 meV FWHM to account for the instrument broadening of 170 meV. The vertical bars indicate the statistical uncertainty of the experiment. The relative population fraction of the initial state was diagnosed to be 82.5% term of configuration 1s²2s²2p and 17.5% ⁴P term of configuration 1s²2s2p². To have the best comparison with the experiment, the theoretical resonance positions have been shifted to lower energy direction by 0.220 eV for –²D, 0.505 eV for –²P, 0.368 eV for –²S, 0.389 eV for ⁴P–, 0.671 eV for ⁴P– and 0.401 eV for ⁴P–.