Photoionization of OIII low-lying states: autoionization resonance energies and widths of some 1s-2p excited states

Twenty-four-state close-coupling calculations are performed on the inner-sh ell photoionization of the terms belonging to the configurations 2s(2)2p(2) and 2s2p(3) of the O III ion. The resonance energies and widths of the tra nsitions of a Is electron excited into the 2p orbital are determined by ana lysing the resonance structures of the photoionization cross sections. The calculations show that the autoionization resonance widths of these inner-s hell transitions are larger than the corresponding Doppler full width at ha lf maximum (FWHM) and Stark FWHM by a factor of two or three under typical plasma conditions (such as a temperature of 10 eV and a density of 0.0016 g cm(-3)). The autoionization resonance broadening is obviously the main bro adening mechanism and should be considered when analysing the plasma spectr um. Only when the electron density is larger than 5 x 10(21) cm(-3) may the Stark FWHM be larger than the autoionization resonance FWHM.