Relativistic 
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-matrix calculations for the electron-impact excitation of neutral molybdenum

Smyth, Ryan; Johnson, Curtis A.; Ennis, D.A.; Loch, S. D.; Ramsbottom, Catherine; Ballance, C. P.

doi:10.1103/physreva.96.042713

Cited by 12 publications

(16 citation statements)

References 19 publications

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“…(b) The a 5 S → z 5 P o excitation cross section in Mo I. The black curve is from [14], red crosses are from [15]. In Figures 7 and 8 we present similar evidence of accuracy and quality for neutral tungsten, with data from Smyth et al [18] (Figures 3 and 6 in their paper).…”

Section: Heavier Systemssupporting

confidence: 76%

“…(a) The a 7 S → z 7 P o excitation cross section in Mo I. The black curve is from [14], red crosses are from [15], and blue circles are from [16]. (b) The a 5 S → z 5 P o excitation cross section in Mo I.…”

Section: Heavier Systemsmentioning

confidence: 99%

“…Measured spectra from the Compact Toroidal Hybrid (CTH) plasma (solid blue line)[17] compared with the theoretical results from[14] (dashed red). The solid black lines show the PEC coefficients for the Mo I transitions, while the dashed red curve shows a theoretical spectrum based upon Gaussian convolved photon emissivity coefficient (PEC) data.…”

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confidence: 99%

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Benchmarking Current Capabilities for the Generation of Excitation and Photoionisation Atomic Data

et al. 2018

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The spectra currently emerging from modern ground- and space-based astronomical instruments are of exceptionally high quality and resolution. To meaningfully analyse these spectra, researchers utilise complex modelling codes to replicate the observations. The main inputs to these codes are atomic data such as excitation and photoionisation cross sections, as well as radiative transition probabilities, energy levels, and line strengths. In this publication, the current capabilities of the numerical methods and computer packages used in the generation of these data are discussed. Particular emphasis is given to Fe-peak species and the heavy systems of tungsten and molybdenum. Some of the results presented to highlight certain issues and/or advances have already been published in the literature, while other sections present new recently evaluated atomic data for the first time.

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Section: Heavier Systemssupporting

confidence: 76%

Section: Heavier Systemsmentioning

confidence: 99%

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Benchmarking Current Capabilities for the Generation of Excitation and Photoionisation Atomic Data

et al. 2018

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“…In lieu of ionization and photon emissivity coefficients from the ADAS database, we consider in this section the ionization coefficient iz and the photon emissivity coefficient ph obtained from the collisional radiative model ColRadPy [18] . These coefficients were derived with an ionization cross-section obtained by the Exchange Classical Impact Parameter (ECIP) method [19] using the energy structure from a non-perturbative Dirac R-matrix calculation performed by Smyth et al [20] to determine the electron impact excitation coefficients. iz and ph exhibit different dependencies on the electron density ( fig.…”

Section: Effects Of the Chodura Sheath On The Spectroscopic Measuremementioning

confidence: 99%

Effects of the Chodura sheath on tungsten ionization and emission in tokamak divertors

Guterl

Johnson

Ennis

et al. 2019

Contributions to Plasma Physics

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The decay of the electric potential in the sheath region in tokamak divertors occurs on a scale length of the order of the main ion gyroradius (Chodura sheath) due to magnetic fields lines intersecting the divertor plates at grazing incidence. As a consequence, high-Z impurities like tungsten ionize within the sheath region in attached plasma conditions. The modification of the electron distribution in the sheath region must thus be taken into account to accurately model ionization and emission of impurities within the sheath region. To that end, an analytical expression of the distribution of the vertical ionization path for impurities sputtered from divertor plasma-facing components is derived. This expression is then used to estimate the fraction of neutral impurities ionizing within the sheath and the average vertical ionization path, and to derive an effective SXB coefficient which includes the effects of the variation of the electron distribution in the sheath region. These results are applied to tungsten impurities sputtered from divertor plates. It is shown that the SXB coefficient for neutral tungsten is significantly reduced in high-density attached divertor plasma conditions ≳ 5 × 10 13 cm −3 because of the ionization of neutral tungsten well within the sheath region.

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“…This was obtained using P. Norrington's updated 1 version of the fully relativistic General-Purpose Relativistic Atomic Structure Program (GRASP 0 ) [6,7]. GRASP 0 has recently been used to model atomic systems as complex as neutral molybdenum [8] and neutral tungsten [9] and the quality of the collisional and radiative data obtained verified by comparison of synthetic spectra and experiment. For this reason, GRASP 0 was a reasonable choice of structure package for this calculation.…”

Section: Atomic Structurementioning

confidence: 99%

Towards the Provision of Accurate Atomic Data for Neutral Iron

et al. 2018

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The rich emission and absorption line spectra of Fe I may be used to extract crucial information on astrophysical plasmas, such as stellar metallicities. There is currently a lack, in quality and quantity, of accurate level-resolved effective electron-impact collision strengths and oscillator strengths for radiative transitions. Here, we discuss the challenges in obtaining an accurate model of the neutral iron atom and compare our theoretical fine-structure energy levels with observation for several increasingly large models. Radiative data is presented for several transitions for which the atomic data is accurately known.

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Relativistic R -matrix calculations for the electron-impact excitation of neutral molybdenum

Cited by 12 publications

References 19 publications

Benchmarking Current Capabilities for the Generation of Excitation and Photoionisation Atomic Data

Benchmarking Current Capabilities for the Generation of Excitation and Photoionisation Atomic Data

Effects of the Chodura sheath on tungsten ionization and emission in tokamak divertors

Towards the Provision of Accurate Atomic Data for Neutral Iron

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