Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VI. Ni II
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Date
2001-11
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Abstract
We present the first detailed ab initio quantum mechanical calculations for total and state-specific recombination rate coefficients for e + Ni III → Ni II. These rates are obtained using a unified treatment
for total electron-ion recombination that treats the nonresonant radiative recombination and the resonant dielectronic recombination in a self-consistent unified manner in the close-coupling approximation.
Large-scale calculations are carried out using a 49 state wavefunction expansion from core configurations 3d^8, 3d^7 4s, and 3d^6 4p that permits the inclusion of prominent dipole allowed core transitions. These extensive calculations for the recombination rates of Ni II required hundreds of CPU hours on the Cray T90. The total recombination rate coefficients are provided for a wide range of temperature. The
state-specific recombination rates for 532 bound states of doublet and quartet symmetries, and the corresponding
photoionization cross sections for leaving the core in the ground state, are presented. Present total recombination rate coefficients differ considerably from the currently used data in astrophysical
models. In particular the enhancement in the low-temperature recombination rate coefficient should help address the long-standing problem of Nickel overabundance in several classes of astronomical objects.
Description
Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.html
Keywords
atomic data, ISM -- general, planetary nebulae -- general
Citation
Nahar, Sultana Nurun, Bautista, Manuel A. "Electron-Ion Recombination Rate Coefficients and Photoionization Cross Sections for Astrophysically Abundant Elements. VI. Ni II," The Astrophysical Journal Supplement Series, v. 137, November, 2001, pp. 201-207.