Retardation (Casimir) energy shifts for Rydberg helium-like low-Z ions

Babb, James F.; Habs, D.; Spruch, Larry; Wolf, A.

doi:10.1007/bf01437395

Cited by 4 publications

(2 citation statements)

References 36 publications

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“…The f level is the highest angular momentum they considered. We extrapolate this quantum defect to higher angular momentum using the predicted l −1 behavior (Babb et al 1992). The resulting resonance energies are listed in Table 2.…”

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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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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“…These states are of interest since they probe the core polarizability [5]. Besides playing an important role in the understanding of low energy capture processes [2, 6È8], they can be used to measure exotic e †ects such as QED retardation (Casimir-like) e †ects associated with the Ðnite speed of light [9].…”

Section: Most Spectroscopic Studies On Highly Charged Ions Deal With ...mentioning

confidence: 99%

Ultraviolet and Visible Spectroscopy of Rydberg States in Highly Ionized Neon

Lapierre¹,

Knystautas

1999

Phys. Scr.

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Ultraviolet and visible beam-foil spectroscopy of Ne at (1800È5300 Ó) 10 MeV reveals many transitions between Rydberg levels with principal quantum numbers 5 O n O 15 in Ne VIÈX. Most of the low-l transitions for the strong ground-state core transition lines in Ne VIII have been observed. Low-l transitions of Ne VI 6È7 and Ne VII 6È7 as well as metastable core-excited quartet Rydberg transitions for Ne VIII 6È7, Ne VIII 7È8 and Ne VIII 8È9 were identiÐed based on multi-conÐguration Hartree-Fock calculations. New transitions between n \ 3 levels have been assigned in Ne VI, VII and IX.

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An Overview of Long-Range Casimir Interactions

Spruch

1993

Long-Range Casimir Forces

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Retardation (Casimir) energy shifts for Rydberg helium-like low-Z ions

Cited by 4 publications

References 36 publications

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

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

Ultraviolet and Visible Spectroscopy of Rydberg States in Highly Ionized Neon

An Overview of Long-Range Casimir Interactions

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