Parameterization of level-resolved RR data fro SPEX

For H-like ions, the quantum-mechanical exact photoionization cross sections for nonrelativistic hydrogenic systems are used to calculate the RR rate coefficients under the principle of detailed balance, while for He-like to Na-like ions, the archival data on ADAS are adopted.

Parameterizations are made for the direct capture rates in a wide temperature range. The fitting accuracies are better than 5% for about 99% of the ~3x10^4^ levels considered here. The ~1% exceptions include levels from low-charged many-electron ions, and/or high-shell (n>~4) levels are less important in terms of interpreting X-ray emitting astrophysical plasmas.