Dielectronic recombination data for dynamic finite-density plasmas - XIII. The magnesium isoelectronic sequence

Department of Physics, University of Strathclyde, Glasgow, Scotland, United Kingdom
Astronomy and Astrophysics (Impact Factor: 4.38). 11/2007; 474(3). DOI: 10.1051/0004-6361:20078238


We have calculated total and partial final- state level- resolved dielectronic recombination ( DR) rate coe. cients for the ground and metastable initial levels of 21 Mg- like ions between Al+ and Xe42+. This is the final part of the assembly of a levelresolved DR database necessary for modelling dynamic finite-density plasmas within the generalized collisional-radiative framework. Calculations have been performed in both LS-and intermediate coupling, allowing for. n = 0 and. n = 1 core- excitations from ground and metastable levels. Complementary partial and total radiative recombination RR coeficients have been calculated for the same ions viz. Al+ through Zn18+, as well as Kr24+, Mo30+, and Xe42+. Fitting coeficients which describe the total RR and DR rate coeficients (separately) are also presented here. Results for a selection of ions fromthis sequence are discussed, and compared with existing theoretical and experimental results. A full set of results can be accessed from the Atomic Data and Analysis Structure (ADAS) database or from the Oak Ridge Controlled Fusion Atomic Data Center ( The complexity of further M-shell sequences, both from the atomic and modelling perspectives, renders this juncture a natural conclusion for the assemblage of the partial database. Further M-shell work, has and will, focus more on total rate coe. cients, rather than partials, at least in the medium term.

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    ABSTRACT: We have investigated the reason for significant discrepancies between the results of two recent, similar computational methods Zatsarinny et al., Astron. Astrophys. 426, 699 2004; Gu, Astrophys. J. 590, 1131 2003 for dielectronic recombination DR of Mg 2+ . It is found that the choice of orbital description can lead to discrepancies by as much as a factor of 2 between total peak DR rate coefficients resulting from otherwise-identical computations. These unexpected differences are attributed to the large sensitivity to bound-orbital relaxation and continuum-orbital description effects on the computed radiative and autoionizing transitions arising from accidental cancellation. In order to obviate these effects, an approach, using a separate, nonor-thogonal orbital basis for each configuration, is employed to yield a DR rate
    Physical Review A 03/2008; 77:032713. DOI:10.1103/PhysRevA.77.032713 · 2.81 Impact Factor
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    ABSTRACT: We have reanalyzed SUMER observations of a parcel of coronal gas using new collisional ionization equilibrium (CIE) calculations. These improved CIE fractional abundances were calculated using state-of-the-art electron-ion recombination data for K-shell, L-shell, Na-like, and Mg-like ions of all elements from H through Zn and, additionally, Al- through Ar-like ions of Fe. They also incorporate the latest recommended electron impact ionization data for all ions of H through Zn. Improved CIE calculations based on these recombination and ionization data are presented here. We have also developed a new systematic method for determining the average emission measure ($EM$) and electron temperature ($T_e$) of an isothermal plasma. With our new CIE data and our new approach for determining average $EM$ and $T_e$, we have reanalyzed SUMER observations of the solar corona. We have compared our results with those of previous studies and found some significant differences for the derived $EM$ and $T_e$. We have also calculated the enhancement of coronal elemental abundances compared to their photospheric abundances, using the SUMER observations themselves to determine the abundance enhancement factor for each of the emitting elements. Our observationally derived first ionization potential (FIP) factors are in reasonable agreement with the theoretical model of Laming (2008).
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    Journal of Physics Conference Series 08/2008; 163(1). DOI:10.1088/1742-6596/163/1/012001
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