  Extensive resonance structures are manifest in R-Matrix (RM) calculations.
However, there exist a large number of highly excited electronic configurations
that may contribute to background non-resonant bound-free opacity in
high-temperature plasmas. Since RM calculations are very complex, and not
essential for background contributions, the Relativistic Distorted Wave (RDW)
method is utilized to complement ("top-up") photoionization cross sections of
Fe XVII obtained using Close-Coupling Breit-Pauli R-Matrix (CC-BPRM) method.
There is good agreement between RDW and BPRM for background cross sections
where resonances are not present, and individual fine structure levels can be
correctly matched spectroscopically, though resonances are neglected in the
RDW. To ensure completeness, a high energy range up to 500 Ry above the
ionization threshold for each level is considered. Interestingly, the
hydrogenic Kramer's approximation also shows the same energy behavior as the
RDW. Grouping separately, the BPRM configurations consist of 454 bound levels
with resonances corresponding to configurations $1s^22s^22p^4nln'l'$ (n $\leq$
3, n' $\leq$ 10); including RDW configurations there are 51,558 levels in
total. The topup contribution results in $\sim$20\% increment, in addition to
the 35\% enhancement from BPRM calculations over the Opacity Project value for
the Rosseland Mean Opacity at the Z-temperature of 2.11 $\times 10^6$K (Pradhan
and Nahar 2017).

Solar and Stellar Astrophysics;Atomic and Molecular Clusters;Atomic Physics