Electric field effects on dielectronic recombination in a collisional-radiative model

Badnell, N. R.; Pindzola, M. S.; Dickson, William J.; Summers, H. P.; Griffin, D. C.; Lang, J.

doi:10.1086/186814

Cited by 28 publications

(33 citation statements)

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“…There are several factors to consider: (i) it appears that while static external fields enhance the DR rate in laboratory experiments on singly ionized ions by several factors [32], the effect on mUltiply charged ions may be much less, as shown in the recent work on C IV where the effective DR rate is estimated to increase at most by 40% [33]; (ii) we have shown that the importance of DR itself, relative to the continuum contribution in the total aR (T), decreases with z due to the dominance of the nuclear over the electronic potential; for example, the Si IX recombination rate coefficients are unlikely to be affected significantly by external fields since the high-n component, subject to the field effects, is smaller than the low-n and the continuum components in nearly the entire temperature range; (iii) the quantitative effect of plasma microfields on autoionization in specific systems is unknown; Stark-field and electron impact ionization of the high-n autoionizing states also need to be taken into account (some discussion in connection with bound states is provided by the recent work by Hummer and Mihalas in their equation-of-state formalism for the Opacity Project…”

Section: Discussionmentioning

confidence: 99%

Unified treatment of electron-ion recombination in the close-coupling approximation

1994

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A unified treatment for electron-ion recombination has been developed and applied to detailed calculations for cross sections and total recombination rate coefficients for a number of atoms and ions. The ab initio calculations are carried out in the close-coupling approximation employing the R-matrix method for the bound and the continuum states of the electron-ion system. All final states of the recombined system are taken into account and the present method subsumes both the radiative and the dielectronic recombination (RR and DR) processes over all energy and temperature ranges of practical importance. Recombined states of the electron-ion system are divided into two groups: (a) n ~ no and (b) no < n ~ 00. Photoionization cross sections are calculated for all bound states of group (a), typically a few hundred bound states, referred to as low-n states, including a detailed energy resolution of the several infinite series of autoionizing resonances converging onto the various excited states of the core ion included in the close-coupling expansion. High-n states of group (b) are treated primarily through the theory of DR developed by Bell and Seaton [J. Phys. B 18, 1589Phys. B 18, (1985]. DR collision strengths with detailed resonance structures are presented. The detailed and the resonance-averaged DR collision strengths show characteristic peaks at the target thresholds of the core ion corresponding to dipoleallowed transitions. Individual bound states of the e +ion system with dominant contribution to lowenergy recombination are described. The present results demonstrate the importance of (i) recombinations to excited states (particularly the metastable states), and (ii) low-energy autoionizing resonances, both of which result in large contributions to effective electron-ion recombination. The individual contributions of the excited bound states of the e + ion system are calculated and their relative contribution to the total are discussed. The general pattern of the recombination rate, as a function of electron temperature, is studied along an isoelectronic sequence. It is found that while the low-energy (temperature) recombination increases with ion charge z, the relative high-energy (temperature) contribution to the total decreases; i.e., viewed as independent processes, the RR part increases while the DR decreases with z. Total recombination rate coefficients for several atoms and ions (C II, S II, C II, N II, 0 III, F IV, N e v, and Si IX) are obtained over the entire temperature range of possible interest in applications. Comparisons are made with earlier works on RR and DR. PACS number(s): 34.80. Kw, 32.80.Dz, 32.80.Fb

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Section: Discussionmentioning

confidence: 99%

Unified treatment of electron-ion recombination in the close-coupling approximation

1994

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“…Finally, we note that use of total zero-density ground-state recombination rate coefficients is, in principle, quite unsafe for the collisional-radiative modelling of dynamic finite-density plasmas -see Burgess & Summers (1969), Summers & Hooper (1983), Badnell et al (1993) and Sect. 4 below.…”

Section: Generalized Collisional-radiative Modellingmentioning

confidence: 99%

“…We do note again that high Rydberg states in a finite density plasma are brought into LTE by (electron) collisions. A preliminary study by Badnell et al (1993) showed that the effect of the plasma microfield on the density-dependent effective recombination rate coefficient was suppressed by collisions driving high Rydberg states into LTE -larger values for the microfield, which lead to larger enhancements of the zero-density rate coefficient, corresponds to denser plasmas for which collisions drive more states into LTE.…”

Section: Experimental Validation Of Dielectronic Recombination Data Amentioning

confidence: 99%

Dielectronic recombination data for dynamic finite-density plasmas

Badnell

O’Mullane

Summers

et al. 2003

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229

282

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Abstract.A programme is outlined for the assembly of a comprehensive dielectronic recombination database within the generalized collisional-radiative (GCR) framework. It is valid for modelling ions of elements in dynamic finite-density plasmas such as occur in transient astrophysical plasmas such as solar flares and in the divertors and high transport regions of magnetic fusion devices. The resolution and precision of the data are tuned to spectral analysis and so are sufficient for prediction of the dielectronic recombination contributions to individual spectral line emissivities. The fundamental data are structured according to the format prescriptions of the Atomic Data and Analysis Structure (ADAS) and the production of relevant GCR derived data for application is described and implemented following ADAS. The requirements on the dielectronic recombination database are reviewed and the new data are placed in context and evaluated with respect to older and more approximate treatments. Illustrative results validate the new high-resolution zero-density dielectronic recombination data in comparison with measurements made in heavy-ion storage rings utilizing an electron cooler. We also exemplify the role of the dielectronic data on GCR coefficient behaviour for some representative light and medium weight elements.

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“…Recent experimental (Bartsch et al 1997(Bartsch et al , 1999Böhm et al 2001Böhm et al , 2002Schippers et al 2000;Gwinner et al 2000), and theoretical studies (Robicheaux & Pindzola 1997;Robicheaux et al 1998;Griffin et al 1998;Mitnik et al 1999) have shown the importance of the effects of crossed external electric and magnetic fields. We expect that low charge Na-like ions will be more sensitive to the external fields, as is the case for Li-like ions (Badnell et al 1993). It was shown that the inclusion of electric field effects gave very good agreement between the intermediate coupling calculations by Griffin et al (1989) and measurements by Andersen et al (1990) of dielectronic recombination for C 3+ and O 5+ , but (crossed) magnetic fields were not considered.…”

Section: Introductionmentioning

confidence: 98%

Dielectronic recombination data for dynamic finite-density plasmas

Altun¹,

Yumak²,

Badnell

et al. 2006

A&A

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Dielectronic recombination (DR) rate coefficients for 22 sodium-like ions, between Mg+ and Xe 43+ , forming magnesium-like ions have been calculated as part of the assembly of a level-resolved DR database necessary for modelling dynamic finite-density plasmas, within the generalized collisional-radiative framework. Calculations have been performed from both ground and metastable initial states, in both LS -and intermediate coupling, allowing for ∆n = 0 and ∆n = 1 core-excitations from ground and metastable levels. Partial and total DR coefficients have been calculated for Mg + to Zn 19+ , as well as Kr 25+ , Mo 31+ , and Xe 43+ . Results for a selection of ions from the sequence are discussed in the paper 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).

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Electric field effects on dielectronic recombination in a collisional-radiative model

Cited by 28 publications

References 0 publications

Unified treatment of electron-ion recombination in the close-coupling approximation

Unified treatment of electron-ion recombination in the close-coupling approximation

Dielectronic recombination data for dynamic finite-density plasmas

Dielectronic recombination data for dynamic finite-density plasmas

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