Electron-Ion Recombination of Fe V
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Date
1999-02
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Abstract
Ionization balance in the low-ionization stages of iron is important in a variety of astrophysical plasmas. Accurate recombination rates are needed but are difficult to compute in a detailed quantum
mechanical treatment. The main difficulty lies in the complexity of strong electron-electron correlation arising due to the open 3d shell. We present the total electron-ion recombination rate coefficients for the
process, e + Fe VI → Fe V, obtained in an ab initio manner. Large-scale computations are carried out in the close coupling (CC) approximation using the R-matrix method employing a unified treatment that
considers the infinite number of states of the recombined ion and incorporates both the radiative recombination (RR) and the dielectronic recombination (DR) processes in a self-consistent manner. It involves
calculations of detailed photoionization cross sections, σ_PI, with autoionizing resonances of a large number of bound states with n ≤ n_max, such as 1054 bound states for the present case of Fe V. The number also equals the total number of state-specific recombination rates obtained for the ion. The high-n states are treated through the DR theory by Bell & Seaton. The same wavefunction expansion is employed in all photoionization/recombination calculations, thereby ensuring self-consistency. Rates are presented at a wide range of temperature for all practical applications. Present rates for total recombination differ considerably from currently used values obtained using simpler approximations. Application of the new recombination rate coefficients and photoionization cross sections for the ionization structure of iron in planetary nebulae show that under typical conditions the relative fractions of Fe V and Fe VI
change by nearly a factor of 2.
Description
Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.html
Keywords
atomic data, atomic processes, planetary nebulae -- general
Citation
Nahar, Sultana Nurun, Bautista, Manuel A. "Electron-Ion Recombination of Fe V," The Astrophysical Journal Supplement Series, v. 120, February, 1999, pp. 327-334.