October 18, 2010, 12:00 pm - 12:30 pm

October 18, 2010, 12:00 pm - 12:30 pm

High Accuracy Radiative Data from the Iron Pro ject for Solar Opacities

Sultana N. Nahar (Ohio State University)

Radiation propagating through a plasma is absorbed and re-emitted by the constituent elements resulting in the opacity effect. Opacity at a photon frequency, the monochromatic opacity, depends primarily on two intrinsic atomic processes, photo-excitation in a bound-bound transition and photoionization in a bound-free transition. However, total monochromatic opacity is obtained from summed contributions of all possible transitions from all ionization stages of all elements in the source. Calculation of accurate parameters for such a large number of transitions has been the key task for obtaining accurate opacities. The need for high precision calculations may be demonstrated by some perplexing results for solar abundances. Recent determination of abundances of the light elements carbon, nitrogen, oxygen etc are up to 30-40% lower than the standard values. Under the Iron Project (IP) we are able to treat a large number of transitions with high accuracy. Of particular interest is the recently found existence of extensive and dominant resonant features in high energy photoionization of iron ions. I will illustrate these and that their inclusion should provide more accurate solar opacities and hence abundances. I will also present new features in low energy photoionization of OII relevant to its abundance in the Orion nebula.

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