The Iron Project \& The Opacity Project: 1.Photoionization of Fe XVII-XVIII for solar plasma opacities

We report the ongoing research at the Ohio State University for determination

of accurate iron opacity at the boundary of the radiative and convection

zones inside the sun. The opacity at the boundary, where Fe XVII-XIX are

most abundant, has been the test  ground for both the theory and experiment.

Opacity  can be obtained from photoionization cross sections and oscillator

strength. To remove or reduce the discrepancy among observed, calculated

and measure opacities, the OSU group has been carrying out high precision

computation for them using relativistic Breit-Pauli R-matrix

(BPRM) method. We will report the updates on the largest calculations for

 photoionization cross sections for Fe~XVII and Fe~XVIII carried out

using  218 and 276 levels of the core ion respectively in their

close coupling wavefunctions. We illustrated features due to high lying

excitations of the core ions, particularly $\Delta n$=1 excitations.

We will show details on convergence features and spectroscopy carried

out for the large number of levels obtained for the two ions. These

will identify the energy levels that are the most dominant contributors

to the opacity.