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 (http://www-cfadc.phy.ornl.gov/data_and_codes). 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.
[Show abstract][Hide abstract] 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
[Show abstract][Hide abstract] ABSTRACT: The relevance of storage-ring electron-ion recombination experiments for
astrophysics is outlined. In particular, the role of low-energy
dielectronic-recombination resonances is discussed. A bibliographic compilation
of electron-ion recombination measurements with cosmically abundant ions is
Journal of Physics Conference Series 08/2008; 163(1). DOI:10.1088/1742-6596/163/1/012001
[Show abstract][Hide abstract] ABSTRACT: Results for electron–ion recombination and photoionization of , with emphasis in high-temperature region, are presented from ab initio unified method. The unified method, based on close coupling (CC) approximation and R-matrix method, (i) subsumes both the radiative recombination (RR) and dielectronic recombination (DR), (ii) enables self-consistent sets of photoionization and recombination cross sections from using an identical wavefunction for both the processes, and (iii) provides state-specific recombination rates of a large number of bound states. A large CC wavefunction expansion, which includes the ground and 28 core excitations of n=2 and 3 complexes and span a wide energy range, has been used. Compared to Δn=2–2, Δn=2–3 core excitations are found to introduce strong resonant structures and enhance the background photoionization cross sections (σPI) in the high-energy region. These features along with prominent photoexcitation-of-core (PEC) resonances at n=3 core thresholds have increased the unified total recombination rate coefficients (αR(T)) at temperatures , region of maximum abundance of the ion in collisional equilibrium, by a factor of 1.6 over previous calculations. State-specific recombination rate coefficients αR(nLS), which include both the RR and DR, are presented for the first time for 685 bound states with n⩽10 and l⩽9. The unified total recombination rate with photoelectron energy αR(E) is presented and the role of low-energy near-threshold fine structure resonances is illustrated. The present results should provide a reasonably complete self-consistent set of recombination rates and photoionization cross sections for astrophysical modelings of high-temperature plasmas from optical to far-ultraviolet wavelength regions.
Journal of Quantitative Spectroscopy and Radiative Transfer 11/2008; DOI:10.1016/j.jqsrt.2008.07.007 · 2.65 Impact Factor
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