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R. P. Bauman, K. B. MacAdam, G. J. Ferland (Univ. of Kentucky)
The primordial abundance of helium and its subsequent production in stars are primarily determined from recombination lines in HII Regions. Accuracies better than a percent must be obtained to make definitive tests of the Big Bang. We report first results of a reinvestigation of the formation of helium recombination lines. Our work builds on previous studies by improving the physical treatment of radiative recombination and the subsequent cascades. We explicitly take fine structure into account by basing our transition rates on the results of Drake [Phys. Rev. A 46, 2378 (1992)]. Previous methodologies were largely based on variational calculations that did not include magnetic and relativistic interactions, thus entailing an unknown degree of inaccuracy. Comparisons with previous calculations are presented along with an assessment of the remaining major uncertainties. This work was supported in part by NSF and NASA.
The author(s) of this abstract have provided an email address for comments about the abstract: bauman@pa.uky.edu