Electron-impact excitation of Cr ii

Wasson, I R; Ramsbottom, Catherine; Norrington, P. H.

doi:10.1051/0004-6361/201015200

Cited by 10 publications

(8 citation statements)

References 14 publications

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“…The theoretical Cr ii model adopted in the present calculation has been described in detail by Wasson et al (2010) and will only be summarized here. A total of 108 LS/280jj levels formed from the basis configurations 3d 5 , 3d 4 4s, and 3d 4 4p 5/2 0 .…”

Section: The Target Modelmentioning

confidence: 99%

“…The earliest sophisticated calculation performed for this ion was reported by Bautista et al (2009) where electronimpact collision strengths for transitions among the lowest 162 fine-structure levels of Cr ii were evaluated but not published. Wasson et al (2010) subsequently extended this calculation and computed the fine-structure collisional data for all forbidden transitions among the lowest 280 levels of Cr ii arising from the basic configurations 3d 5 , 3d 4 4s, and 3d 4 4p. This latter calculation corresponded to a substantial 1932 coupled channel problem.…”

Section: Introductionmentioning

confidence: 99%

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ELECTRON-IMPACT EXCITATION OF Cr II: A THEORETICAL CALCULATION OF EFFECTIVE COLLISION STRENGTHS FOR OPTICALLY ALLOWED TRANSITIONS

Wasson

Ramsbottom

Scott

2011

ApJS

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In this paper, we present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for the complicated iron-peak ion Cr ii. We consider specifically the allowed lines for transitions from the 3d 5 and 3d 4 4s even parity configuration states to the 3d 4 4p odd parity configuration levels. The parallel suite of R-Matrix packages, RMATRX II, which have recently been extended to allow for the inclusion of relativistic effects, were used to compute the collision cross sections. A total of 108 LSπ/280 Jπ levels from the basis configurations 3d 5 , 3d 4 4s, and 3d 4 4p were included in the wavefunction representation of the target including all doublet, quartet, and sextet terms. Configuration interaction and correlation effects were carefully considered by the inclusion of seven more configurations and a pseudo-corrector 4d type orbital. The 10 configurations incorporated into the Cr ii model thus listed are 3d 5 , 3d 4 4s, 3d 4 4p, 3d 3 4s 2 , 3d 3 4p 2 , 3d 3 4s4p, 3d 4 4d, 3d 3 4s4d, 3d 3 4p4d, and 3d 3 4d 2 , constituting the largest Cr ii target model considered to date in a scattering calculation. The Maxwellian averaged effective collision strengths are computed for a wide range of electron temperatures 2000-100,000 K which are astrophysically significant. Care has been taken to ensure that the partial wave contributions to the collision strengths for these allowed lines have converged with "top-up" from the Burgess-Tully sum rule incorporated. Comparisons are made with the results of Bautista et al. and significant differences are found for some of the optically allowed lines considered.

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Section: The Target Modelmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

ELECTRON-IMPACT EXCITATION OF Cr II: A THEORETICAL CALCULATION OF EFFECTIVE COLLISION STRENGTHS FOR OPTICALLY ALLOWED TRANSITIONS

Wasson

Ramsbottom

Scott

2011

ApJS

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“…The external region calculations were performed with the pstgf code (Ballance & Griffin ). These codes have been successfully utilized over the last number of years to compute complete and accurate sets of atomic data for other complex Fe‐peak systems such as Fe ii (Ramsbottom, Hudson & Norrington ; Ramsbottom ), Ni ii (Cassidy, Ramsbottom & Scott ) and Cr ii (Wasson, Ramsbottom & Scott , ).…”

Section: Introductionmentioning

confidence: 99%

Electron-impact excitation of Sc ii: collision strengths and effective collision strengths for fine-structure transitions

Grieve

Ramsbottom

2012

Monthly Notices of the Royal Astronomical Society

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Accurate fine-structure atomic data for the Fe-peak elements are essential for interpreting astronomical spectra. There is a severe paucity of data available for Sc II, highlighted by the fact that no collision strengths are readily available for this ion. We present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for Sc II. The collision strengths were calculated for all 3916 transitions amongst 89 jj levels (arising from the 3d4s, 3d 2 , 4s 2 , 3d4p, 4s4p, 3d5s, 3d4d, 3d5p, 4p 2 and 3d4f configurations), resulting in a 944 coupled channel problem. The R-matrix package RMATRXII was utilized, along with the transformation code FINE and the external region code PSTGF, to calculate the collision strengths for a range of incident electron energies in the 0 to 8.3 Rydberg region. Maxwellian averaged effective collision strengths were then produced for 27 temperatures lying within the astrophysically significant range of 30 to 10 5 K.The collision strengths and effective collision strengths were produced for two different target models. The purpose was to systematically examine the effect of including open 3p correlation terms into the configuration interaction expansion for the wavefunction. The first model consisted of all 36 CI terms that could be generated with the 3p core closed. The second model incorporated an additional six configurations which allowed for single-electron excitations from within the 3p core. Comparisons are made between the two models and the results of Bautista et al., obtained by private communication. It is concluded that the first model produced the most reliable set of collision and effective collision strengths for use in astrophysical and plasma applications.

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“…Furthermore, the need for accurate atomic data for Cr ii has also been pointed out by Dimitrijevic et al (2007) for stellar abundance studies and by Wasson, Ramsbottom & Norrington (2010) for calculation of collision strengths.…”

Section: Introductionmentioning

confidence: 99%

The FERRUM project: metastable lifetimes in Cr ii

Bäckström

Gurell

Royen

et al. 2011

Monthly Notices of the Royal Astronomical Society

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Parity forbidden radiative transitions from metastable levels are observed in spectra of low‐density astrophysical plasmas. These lines are used as probes of the physical conditions, made possible due to the long lifetime of their upper level. In a joint effort, the FERRUM project aims to obtain new and accurate atomic data for the iron‐group elements, and part of this project concerns forbidden lines. The radiative lifetimes of the metastable energy levels 3 d4(a 3 D)4 s c4 D 5/2 and 3 d4(a 3 D)4 s c4 D 7/2 of singly ionized chromium have been measured. The experiment has been performed at the ion storage ring CRYRING. We employed a laser‐probing technique developed for measuring long lifetimes. In this article, we present the lifetimes of these levels to be τ5/2= 1.28(16) s and τ7/2= 1.37(7) s, respectively. A comparison with previous theoretical work shows good agreement and the result is discussed in a theoretical context.

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Electron-impact excitation of Cr ii

Cited by 10 publications

References 14 publications

ELECTRON-IMPACT EXCITATION OF Cr II: A THEORETICAL CALCULATION OF EFFECTIVE COLLISION STRENGTHS FOR OPTICALLY ALLOWED TRANSITIONS

ELECTRON-IMPACT EXCITATION OF Cr II: A THEORETICAL CALCULATION OF EFFECTIVE COLLISION STRENGTHS FOR OPTICALLY ALLOWED TRANSITIONS

Electron-impact excitation of Sc ii: collision strengths and effective collision strengths for fine-structure transitions

The FERRUM project: metastable lifetimes in Cr ii

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