Recombination of with free electrons at very low energies

Hoffknecht, A.; Uwira, O.; Schennach, S.; Frank, A.; Haselbauer, J.; Spies, W.; Angert, N.; Mokler, P. H.; Becker, R.; Kleinod, M.; Schippers, S.; Müller, A.

doi:10.1088/0953-4075/31/10/026

Cited by 46 publications

(49 citation statements)

References 31 publications

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“…As already mentioned, the explicit inclusion of all these resonance levels in the configuration expansions is not possible due to practical limitations. In this situation Flambaum et al (2002) have applied statistical theory to electron ion recombination and achieved good agreement with the experimental low-energy recombination rate coefficients for Au 25+ of Hoffknecht et al (1998). In statistical theory (Flambaum et al 2002), only a limited number of "doorway" resonance levels are considered in the initial dielectronic capture process.…”

Section: Exotic Recombination Pathwaysmentioning

confidence: 84%

“…An example, for such a system is the open-4 f -shell ion Au 25+ ([Kr] 4d 10 4 f 8 ). Experimentally, recombination of Au 25+ has been studied by Hoffknecht et al (1998) who used a single-pass electron-ion merged-beam approach at the UNILAC linear accelerator at GSI in Darmstadt, Germany. In these experiments an exceptionally large recombination rate coefficient was observed at zero electron-ion collision energy, exceeding the expectation for nonresonant radiative recombination (RR) by more than two orders of magnitude.…”

Section: Exotic Recombination Pathwaysmentioning

confidence: 99%

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Electron–ion merged-beam experiments at heavy-ion storage rings

Schippers

2015

Nuclear Instruments and Methods in Physics Research Section B:

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In the past two decades, the electron-ion merged-beams technique has extensively been exploited at heavy-ion storage rings equipped with electron coolers for spectroscopic studies of highly charged ions as well as for measuring absolute cross sections and rate coefficients for electron-ion recombination and electron-impact ionization of multiply charged atoms ions. Some recent results are highlighted and future perspectives are pointed out, in particular, in view of novel experimental possibilities at the FAIR facility in Darmstadt and at the Cryogenic Storage Ring at the Max-PlanckInstitute for Nuclear Physics in Heidelberg.

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Section: Exotic Recombination Pathwaysmentioning

confidence: 84%

Section: Exotic Recombination Pathwaysmentioning

confidence: 99%

Electron–ion merged-beam experiments at heavy-ion storage rings

Schippers

2015

Nuclear Instruments and Methods in Physics Research Section B:

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“…k B T e remain to be resolved (Hoffknecht et al 1998;Schippers et al 1998;Gwinner et al 2000;Hoffknecht et al 2001), but it is highly unlikely that their resolution will lead to a near 0 eV recombination rate coefficient that increases by a factor of %30 for a change in ionic charge from 17 to 19. Thus, we infer that there are unresolved DR resonances lying at energies below 0.015 eV.…”

Section: Resultsmentioning

confidence: 99%

Dielectronic Recombination (viaN = 2→N′ = 2 Core Excitations) and Radiative Recombination of Fexx: Laboratory Measurements and Theoretical Calculations

Savin

Behar

Kahn

et al. 2002

ASTROPHYS J SUPPL S

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We have measured the resonance strengths and energies for dielectronic recombination (DR) of Fe xx forming Fe xix via N ¼ 2 ! N 0 ¼ 2 (DN ¼ 0) core excitations. We have also calculated the DR resonance strengths and energies using the AUTOSTRUCTURE, Hebrew University Lawrence Livermore Atomic Code (HULLAC), Multiconfiguration Dirac-Fock (MCDF), and R-matrix methods, four different state-ofthe-art theoretical techniques. On average the theoretical resonance strengths agree to within .10% with experiment. The AUTOSTRUCTURE, MCDF, and R-matrix results are in better agreement with experiment than are the HULLAC results. However, in all cases the 1 standard deviation for the ratios of the theoretical-to-experimental resonance strengths is &30%, which is significantly larger than the estimated relative experimental uncertainty of .10%. This suggests that similar errors exist in the calculated level populations and line emission spectrum of the recombined ion. We confirm that theoretical methods based on inverse-photoionization calculations (e.g., undamped R-matrix methods) will severely overestimate the strength of the DR process unless they include the effects of radiation damping. We also find that the coupling between the DR and radiative recombination (RR) channels is small.Below 2 eV the theoretical resonance energies can be up to %30% larger than experiment. This is larger than the estimated uncertainty in the experimental energy scale (.0.5% below %25 eV and .0.2% for higher energies) and is attributed to uncertainties in the calculations. These discrepancies makes DR of Fe xx an excellent case for testing atomic structure calculations of ions with partially filled shells. Above 2 eV, agreement between the theoretical and measured energies improves dramatically with the AUTOSTRUC-TURE and MCDF results falling within 2% of experiment, the R-matrix results within 3%, and HULLAC within 5%. Agreement for all four calculations improves as the resonance energy increases.We have used our experimental and theoretical results to produce Maxwellian-averaged rate coefficients for DN ¼ 0 DR of Fe xx. For k B T e & 1 eV, which includes the predicted formation temperatures for Fe xx in an optically thin, low-density photoionized plasma with cosmic abundances, the experimental and theoretical results agree to better than %15%. This is within the total estimated experimental uncertainty limits of .20%. Agreement below %1 eV is difficult to quantify due to current theoretical and experimental limitations. Agreement with previously published LS-coupling rate coefficients is poor, particularly for k B T e . 80 eV. This is attributed to errors in the resonance energies of these calculations as well as the omission of DR via 2p 1=2 ! 2p 3=2 core excitations. We have also used our R-matrix results, topped off using AUTOSTRUC-TURE for RR into J ! 25 levels, to calculate the rate coefficient for RR of Fe xx. Our RR results are in good agreement with previously published calculations. We find that for temperatures as low as k B T e % 10...

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“…The ion charge state had been chosen because W 20+ is isoelectronic with Au 25+ , for which previous experiments [90] had shown excessive recombination rate coefficients. Indeed, recombination of W 20+ ions reached up to about 2 × 10 −6 cm 3 s −1 at 1 meV relative energy.…”

Section: Electron-ion Recombinationmentioning

confidence: 99%

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

Müller

2015

Atoms

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Collisional processes and details of atomic structure of heavy many-electron atoms and ions are not yet understood in a fully satisfying manner. Experimental studies are required for guiding new theoretical approaches. In response to fusion-related needs for collisional and spectroscopic data on tungsten atoms in all charge states, a project has been initiated in which electron-impact and photon-induced ionization as well as photorecombination of W q+ ions are studied. Cross sections and rate coefficients were determined for charge states q ranging from q = 1 to q = 5 for photoionization, for q = 1 up to q = 19 for electron-impact ionization and for q = 18 to q = 21 for electron-ion recombination. An overview, together with a critical assessment of the methods and results is provided.

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Recombination of with free electrons at very low energies

Cited by 46 publications

References 31 publications

Electron–ion merged-beam experiments at heavy-ion storage rings

Electron–ion merged-beam experiments at heavy-ion storage rings

Dielectronic Recombination (viaN = 2→N′ = 2 Core Excitations) and Radiative Recombination of Fexx: Laboratory Measurements and Theoretical Calculations

Fusion-Related Ionization and Recombination Data for Tungsten Ions in Low to Moderately High Charge States

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