Claudio Mendoza (IVIC, Caracas, and CeCalCULA, CPTM, Mérida, Venezuela)
The reliability of the atomic data required in astrophysical applications, in particular in abundance determinations, has been a perennial concern to the few research groups that cater for this well-established data demand. In this respect, oxygen ions are useful study cases due to their simple atomic structures, result of low atomic (Z=8) and electron (1 ≤ N ≤ 8) numbers, from which handy plasma diagnostics have been devised and widely used to take advantage of the high oxygen cosmic abundances and readily identifiable spectral features.
The data reliability issue has recently been brought to the limelight due to the downward revision of the oxygen solar abundance, which questions the accuracy of its opacity at the base of the convection zone, and in the context of the huge discrepancies between the oxygen abundance in gaseous nebulae obtained from diagnostics using either recombination or collisionally excited lines.
In the present talk we discuss the inherent difficulties encountered in the computations of both radiative and collisional atomic data for oxygen ionic species, and how they impact data accuracy and plasma diagnostics. We make special reference to the damping (radiative and Auger) effects involved in inner-shell K absorption, and how they could affect the oxygen opacity and the abundance determinations in the interstellar medium from X-ray spectra.