Dielectronic Recombination of Fe XIX Forming Fe XVIII: Laboratory Measurements and Theoretical Calculations

Details Dielectronic Recombination of Fe XIX Forming Fe XVIII: Laboratory Measurements and Theoretical Calculations Dielectronic Recombination of Fe XIX Forming Fe XVIII: Laboratory Measurements and Theoretical Calculations

Sep 2002

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002apj...576.1098s&link_type=abstract

The Astrophysical Journal, Volume 576, Issue 2, pp. 1098-1107.

Astronomy and Astrophysics

Astronomy

31

Atomic Data, Atomic Processes, Methods: Laboratory

Scientific paper

We have measured resonance strengths and energies for dielectronic recombination (DR) of Fe XIX forming Fe XVIII via N=2-->N'=2 and N=2-->N'=3 core excitations. All measurements were carried out using the heavy-ion Test Storage Ring at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. We have also calculated these resonance strengths and energies using two independent, state-of-the-art techniques: the perturbative multiconfiguration Breit-Pauli (MCBP) and multiconfiguration Dirac-Fock (MCDF) methods. Overall, reasonable agreement is found between our experimental results and theoretical calculations. The most notable discrepancies are for the 3l3l' resonances. The calculated MCBP and MCDF resonance strengths for the n=3 complex lie, respectively, ~47% and ~31% above the measured values. These discrepancies are larger than the estimated <~20% total experimental uncertainty in our measurements. We have used our measured 2-->2 and 2-->3 results to produce a Maxwellian-averaged rate coefficient for DR of Fe XIX. Our experimentally derived rate coefficient is estimated to be good to better than ~20% for kBTe>=1 eV. Fe XIX is predicted to form in photoionized and collisionally ionized cosmic plasmas at kBTe>>1 eV. Hence, our rate coefficient is suitable for use in ionization balance calculations of these plasmas. Previously published theoretical DR rate coefficients are in poor agreement with our experimental results. None of these published calculations reliably reproduce the magnitude or temperature dependence of the experimentally derived rate coefficient. Our MCBP and MCDF results agree with our experimental rate coefficient to within ~20%.

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