Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 +: laboratory measurements and theoretical calculations

M. Lestinsky, Nigel Badnell, D. Bernhardt, D. Bing, M. Grieser, M. Hahn, J. Hoffmann, B. Jordon-Thaden, C. Krantz, O. Novotný, D.A. Orlov, R. Repnow, A. Shornikov, A. Müller, S Schippers, A. Wolf, D. W. Savin

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

We have measured electron–ion recombination for C-like Mg6+ forming Mg5+, and for B-like Mg7+ forming Mg6+. These studies were performed using a merged electron–ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg6+ results, we find that the majority of the stored ions are in a metastable level, while for Mg7+ the metastable fraction is insignificant. We present the Mg6+ merged beams recombination rate coefficient for DR via N = 2 → N = 2 core electron excitations (ΔN = 0 DR) and for Mg7+ via 2 → 2 and 2 → 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit–Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for ΔN = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg6+ ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg7+ and we present an experimentally derived Mg7+ PRRC for plasma temperatures from 400 K to 107 K with an estimated uncertainty of less than 27% at a 90% confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.
LanguageEnglish
Article number40
Number of pages13
JournalAstrophysical Journal
Volume40
Issue number1
DOIs
Publication statusPublished - 24 Sep 2012

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electron-ion recombination
recombination
electron
ion
coefficients
plasma
ions
ion beams
ion storage
plasma temperature
Germany
excitation
confidence
heavy ions
cascades
electrons
stabilization
laboratory
calculation
electron beams

Keywords

  • atomic data
  • atomic processes
  • electron-ion recombination
  • plasma recombination rate coefficient
  • plasma temperature
  • plasma modelling codes
  • cosmic atomic plasma
  • ionization balance calculations
  • dielectronic recombination

Cite this

Lestinsky, M. ; Badnell, Nigel ; Bernhardt, D. ; Bing, D. ; Grieser, M. ; Hahn, M. ; Hoffmann, J. ; Jordon-Thaden, B. ; Krantz, C. ; Novotný, O. ; Orlov, D.A. ; Repnow, R. ; Shornikov, A. ; Müller, A. ; Schippers, S ; Wolf, A. ; Savin, D. W. / Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 + : laboratory measurements and theoretical calculations. In: Astrophysical Journal. 2012 ; Vol. 40, No. 1.
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title = "Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 +: laboratory measurements and theoretical calculations",
abstract = "We have measured electron–ion recombination for C-like Mg6+ forming Mg5+, and for B-like Mg7+ forming Mg6+. These studies were performed using a merged electron–ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg6+ results, we find that the majority of the stored ions are in a metastable level, while for Mg7+ the metastable fraction is insignificant. We present the Mg6+ merged beams recombination rate coefficient for DR via N = 2 → N = 2 core electron excitations (ΔN = 0 DR) and for Mg7+ via 2 → 2 and 2 → 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit–Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for ΔN = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg6+ ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg7+ and we present an experimentally derived Mg7+ PRRC for plasma temperatures from 400 K to 107 K with an estimated uncertainty of less than 27{\%} at a 90{\%} confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.",
keywords = "atomic data, atomic processes, electron-ion recombination, plasma recombination rate coefficient, plasma temperature, plasma modelling codes, cosmic atomic plasma, ionization balance calculations, dielectronic recombination",
author = "M. Lestinsky and Nigel Badnell and D. Bernhardt and D. Bing and M. Grieser and M. Hahn and J. Hoffmann and B. Jordon-Thaden and C. Krantz and O. Novotn{\'y} and D.A. Orlov and R. Repnow and A. Shornikov and A. M{\"u}ller and S Schippers and A. Wolf and Savin, {D. W.}",
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Lestinsky, M, Badnell, N, Bernhardt, D, Bing, D, Grieser, M, Hahn, M, Hoffmann, J, Jordon-Thaden, B, Krantz, C, Novotný, O, Orlov, DA, Repnow, R, Shornikov, A, Müller, A, Schippers, S, Wolf, A & Savin, DW 2012, 'Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 +: laboratory measurements and theoretical calculations' Astrophysical Journal, vol. 40, no. 1, 40. https://doi.org/10.1088/0004-637X/758/1/40

Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 + : laboratory measurements and theoretical calculations. / Lestinsky, M.; Badnell, Nigel; Bernhardt, D.; Bing, D.; Grieser, M.; Hahn, M.; Hoffmann, J.; Jordon-Thaden, B.; Krantz, C.; Novotný, O.; Orlov, D.A.; Repnow, R.; Shornikov, A.; Müller, A.; Schippers, S ; Wolf, A.; Savin, D. W.

In: Astrophysical Journal, Vol. 40, No. 1, 40, 24.09.2012.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Electron-ion recombination of Mg6 + forming Mg5 + and of Mg7 + forming Mg6 +

T2 - Astrophysical Journal

AU - Lestinsky, M.

AU - Badnell, Nigel

AU - Bernhardt, D.

AU - Bing, D.

AU - Grieser, M.

AU - Hahn, M.

AU - Hoffmann, J.

AU - Jordon-Thaden, B.

AU - Krantz, C.

AU - Novotný, O.

AU - Orlov, D.A.

AU - Repnow, R.

AU - Shornikov, A.

AU - Müller, A.

AU - Schippers, S

AU - Wolf, A.

AU - Savin, D. W.

PY - 2012/9/24

Y1 - 2012/9/24

N2 - We have measured electron–ion recombination for C-like Mg6+ forming Mg5+, and for B-like Mg7+ forming Mg6+. These studies were performed using a merged electron–ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg6+ results, we find that the majority of the stored ions are in a metastable level, while for Mg7+ the metastable fraction is insignificant. We present the Mg6+ merged beams recombination rate coefficient for DR via N = 2 → N = 2 core electron excitations (ΔN = 0 DR) and for Mg7+ via 2 → 2 and 2 → 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit–Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for ΔN = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg6+ ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg7+ and we present an experimentally derived Mg7+ PRRC for plasma temperatures from 400 K to 107 K with an estimated uncertainty of less than 27% at a 90% confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.

AB - We have measured electron–ion recombination for C-like Mg6+ forming Mg5+, and for B-like Mg7+ forming Mg6+. These studies were performed using a merged electron–ion beam arrangement at the TSR heavy ion storage ring located in Heidelberg, Germany. Both primary ions have metastable levels with significant lifetimes. Using a simple cascade model we estimate the population fractions in these metastable levels. For the Mg6+ results, we find that the majority of the stored ions are in a metastable level, while for Mg7+ the metastable fraction is insignificant. We present the Mg6+ merged beams recombination rate coefficient for DR via N = 2 → N = 2 core electron excitations (ΔN = 0 DR) and for Mg7+ via 2 → 2 and 2 → 3 core excitations. Taking the estimated metastable populations into account, we compare our results to state-of-the-art multiconfiguration Breit–Pauli theoretical calculations. Significant differences are found at low energies where theory is known to be unreliable. Moreover, for both ions we observe a discrepancy between experiment and theory for ΔN = 0 DR involving capture into high-n Rydberg levels and where the stabilization is primarily due to a radiative transition of the excited core electron. This is consistent with previous DR experiments on M-shell iron ions which were performed at TSR. The large metastable content of the Mg6+ ion beam precludes generating a plasma recombination rate coefficient (PRRC). However, this is not an issue for Mg7+ and we present an experimentally derived Mg7+ PRRC for plasma temperatures from 400 K to 107 K with an estimated uncertainty of less than 27% at a 90% confidence level. We also provide a fit to our experimentally derived PRRC for use in plasma modeling codes.

KW - atomic data

KW - atomic processes

KW - electron-ion recombination

KW - plasma recombination rate coefficient

KW - plasma temperature

KW - plasma modelling codes

KW - cosmic atomic plasma

KW - ionization balance calculations

KW - dielectronic recombination

UR - http://iopscience.iop.org/journal/0004-637X

U2 - 10.1088/0004-637X/758/1/40

DO - 10.1088/0004-637X/758/1/40

M3 - Article

VL - 40

JO - Astrophysical Journal

JF - Astrophysical Journal

SN - 0004-637X

IS - 1

M1 - 40

ER -