Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. XI. N V-VI and F VII-VIII for Ultraviolet and X-Ray Modeling
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Date
2006-05
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Abstract
The inverse processes of photoionization and electron-ion recombination for hv + N V ↔ N VI + e, hv + N VI ↔ N VII + e, hv + F VII ↔ F VIII + e, and hv + F VIII ↔ F IX + e are studied in detail using a self-consistent
unified method for the total electron-ion recombination. The method enables calculation of the total and level-specific
recombination rate coefficients α_R and α_R(i), subsuming both radiative and dielectronic recombination (RR and DR). The photoionization and recombination cross sections σ_PI and σ_RC are computed using an identical wave function expansion for both processes in the close coupling approximation using the R-matrix method. The results include total and partial photoionization cross sections and recombination rate coefficients for all fine-structure levels up to n ≤ 10, about 100 for Li-like N V and F VII with 1/2 ≤ J ≤ 17/2, and over 170 for He-like N VI and F VIII with 0 ≤ J ≤ 10. Level-specific σ_PI(nSLJ ) and α_R(T; nSLJ ) are calculated for the first time for these ions. The
coupled-channel wave function expansions for N V and F VII consist of 17 levels of cores N VI and F VIII, respectively, and for N VI and F VIII consist of 16 levels of cores N VII and F IX, respectively. Relativistic fine structure is considered through the Breit-Pauli R-matrix method. The single-valued total α_R(T) is presented over an extended temperature range for astrophysical and laboratory plasma applications. Although the total unified α_R(T) for all ions
agree well with the available published RR+DR rates, significant differences are noted at the DR peak for N v. Total α_RC(E) and α_R(E) as functions of photoelectron energy are presented for comparison with experiments. Total rates for H-like N VII and F IX are also given for completeness. The cross sections σ_PI and σ_RC include important atomic effects such as radiation damping, channel couplings, and interference of DR and RR, and should be accurate to
within 10%-15%. The comprehensive data sets are applicable for ionization balance and recombination-cascade models for UV and X-ray lines.
Description
Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.html
Keywords
atomic data, atomic processes, line -- formation, X-rays -- general
Citation
Nahar, Sultana Nurun. "Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. XI. N V-VI and F VII-VIII for Ultraviolet and X-Ray Modeling," The Astrophysical Journal Supplement Series, v. 164, May, 2006, pp. 280-296.