APED

APED is designed to be used by APEC, the Astrophysical Plasma Emission Code. APEC reads the APED data and calculates the emission spectrum of a hot plasma, either in collisional ionization equilibrium (CIE) or for a model non-ionization equilibrium (NEI) plasma. (Scientific use of NEI models is pending completion of the compilation of recombination rates in APED.) Our primary temperature range is 2.5 10^4 to 8.0 10^8 Kelvin.

A major advantage of using the astronomical standard FITS format is that the original references for all atomic data can be included in APED, and can be easily accessed by users. If a user determines that a result depends critically upon certain atomic data, she can find the original publication of that data or, for unpublished data, the original authors can be contacted as needed.

Data compilation is the most difficult task. Our group is concentrating on calculations relevant to X-ray astronomy. Most of the data currently in APED for the UV and EUV spectral bands are courtesy of the Chianti project. The iron L shell data in APED are calculated by Duane Liedahl using HULLAC, with other L shell data currently being processed. Much of the data for the Hydrogen- and Helium-like ions are from the papers of H. Zhang and D. Sampson. We plan to include all atoms with Z=1-30, but are concentrating on the astrophysically abundant ions first: H, He, C, N, O, Ne, Mg, Al, Si, S, Ar, Ca, Fe, and Ni. We are compiling data in the following categories:

1. Wavelengths: Wavelengths are generated from the energy levels computed for electron impact excitation; however, these wavelengths are not usually accurate enough for high resolution spectroscopic work. Therefore, we are also compiling accurate wavelengths, either from QED atomic calculations, in the case of H- and He-like ions, or from laboratory measurements.
2. Effective collision strengths: The collisional (de-) excitation rate coefficient between two levels of an ion, both due to electron-ion collisions and proton-ion collisions.
3. Atomic transition probabilities: Einstein A-values are included.
4. Dielectronic recombination: Satellite line wavelengths and level-to-level recombination rates are used. Although data giving both the doubly-excited initial state and the singly-excited final state are most useful, results giving just the satellite line wavelength and its relative power can also be useful.
5. Partial photoionization rates from ground and excited states: We have the ground state data from the Opacity Project for all ions. However, the radiative recombination rates to excited levels requires the photoionization rate from that level.
6. Total ionization and recombination rates: These are used to calculate the ionization balance.
7. Error estimates: Error estimates on atomic data are useful for spectral modeling.