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R.P. Bauman, G.J. Ferland, K.B. MacAdam (University of Kentucky)
Hydrogen and helium recombination emission lines are used to determine chemical abundances and physical conditions in a variety of objects, and form the foundation for much of our understanding of the chemical evolution of the Universe. We are developing basic software tools needed for the modeling of the atomic physics of H-like and He-like ions. Here we present Open Source codes for H-like ions (without fine-structure) for the calculation of atomic transition probabilities, photoionization cross-sections, and radiative recombination rate coefficients. These quantities are based on the well known analytical forms of the solutions of the hydrogenic dipole radial integral for bound-bound and bound-free transitions. The results for He-like ions will follow shortly.
Although the needed radiative rates are known to high precision, the collisional rate coefficients involving higher levels of H and He are uncertain by factors of 2 to 3. These introduce 5-20 percent uncertainties in optical and infrared lines for some conditions. Our codes will be made publicly available so that anyone can check the effects of other collisional rates on observed lines, with the hope of promoting further work. The codes may be found at http://nimbus.pa.uky.edu/hydrogen. This project is supported by the NSF and NASA through grants AST 0071180 and NAG5-8212.
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The author(s) of this abstract have provided an email address for comments about the abstract: bauman@pa.uky.edu