Collisional-radiative calculations of He line emission in low-temperature plasmas

C. P. Ballance, D. C. Griffin, S. D. Loch, R. F. Boivin, M. S. Pindzola

Research output: Chapter in Book/Report/Conference proceedingChapter

14 Citations (Scopus)

Abstract

We present spectral modeling results for neutral helium. Our underlying atomic data contains radiative transition rates that are generated from atomic structure calculations and electron-impact excitation rates, that are determined from both the standard R-matrix method and the R-matrix with pseudostates RMPS method. In this paper, we focus on transitions of particular importance to diagnostic line ratios. For example, our calculated rate coefficient for the electron-impact transition 1s3s 1S→1s3p 1P, which has a pronounced effect on the 728.1 nm diagnostic spectral line, is found to be in good agreement with previous experimental mea- surements. We also consider transitions from the 1s2 1S ground and 1s2s 3S terms to terms of the n=4 shell. They are found to be affected significantly by coupling of the bound states to the target continuum continuum coupling, which is included in our RMPS calculation, but not in our standard R-matrix calculation. We perform collisional-radiative calculations to determine spectral line intensity ratios for three ratios of particular interest, namely the 504.8 nm/471.3 nm, 492.2 nm/471.3 nm, and 492.2 nm/504.8 nm line ratios. Comparing our results determined from the RMPS excitation rates with those from the standard R-matrix excitation rates, we find that continuum coupling affects the rate coefficients significantly, leading to different values for all three line ratios. We also compare our modeling results with spectral measurements taken recently on the Auburn Helicon plasma device, finding that the ground and metastable populations are not in equilibrium, and that the experimental measurements are more consistent with the 1s2s 3S metastable term populations being short lived in the plasma.
Original languageEnglish
Title of host publicationPhysical Review A - Atomic, Molecular, and Optical Physics
DOIs
Publication statusPublished - 2006

Publication series

NamePhysical Review A - Atomic, Molecular, and Optical Physics
Volume74

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cold plasmas
continuums
electron impact
line spectra
excitation
coefficients
atomic structure
matrix methods
helium

Cite this

Ballance, C. P., Griffin, D. C., Loch, S. D., Boivin, R. F., & Pindzola, M. S. (2006). Collisional-radiative calculations of He line emission in low-temperature plasmas. In Physical Review A - Atomic, Molecular, and Optical Physics (Physical Review A - Atomic, Molecular, and Optical Physics; Vol. 74). https://doi.org/10.1103/PhysRevA.74.012719
Ballance, C. P. ; Griffin, D. C. ; Loch, S. D. ; Boivin, R. F. ; Pindzola, M. S. / Collisional-radiative calculations of He line emission in low-temperature plasmas. Physical Review A - Atomic, Molecular, and Optical Physics. 2006. (Physical Review A - Atomic, Molecular, and Optical Physics).
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abstract = "We present spectral modeling results for neutral helium. Our underlying atomic data contains radiative transition rates that are generated from atomic structure calculations and electron-impact excitation rates, that are determined from both the standard R-matrix method and the R-matrix with pseudostates RMPS method. In this paper, we focus on transitions of particular importance to diagnostic line ratios. For example, our calculated rate coefficient for the electron-impact transition 1s3s 1S→1s3p 1P, which has a pronounced effect on the 728.1 nm diagnostic spectral line, is found to be in good agreement with previous experimental mea- surements. We also consider transitions from the 1s2 1S ground and 1s2s 3S terms to terms of the n=4 shell. They are found to be affected significantly by coupling of the bound states to the target continuum continuum coupling, which is included in our RMPS calculation, but not in our standard R-matrix calculation. We perform collisional-radiative calculations to determine spectral line intensity ratios for three ratios of particular interest, namely the 504.8 nm/471.3 nm, 492.2 nm/471.3 nm, and 492.2 nm/504.8 nm line ratios. Comparing our results determined from the RMPS excitation rates with those from the standard R-matrix excitation rates, we find that continuum coupling affects the rate coefficients significantly, leading to different values for all three line ratios. We also compare our modeling results with spectral measurements taken recently on the Auburn Helicon plasma device, finding that the ground and metastable populations are not in equilibrium, and that the experimental measurements are more consistent with the 1s2s 3S metastable term populations being short lived in the plasma.",
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Ballance, CP, Griffin, DC, Loch, SD, Boivin, RF & Pindzola, MS 2006, Collisional-radiative calculations of He line emission in low-temperature plasmas. in Physical Review A - Atomic, Molecular, and Optical Physics. Physical Review A - Atomic, Molecular, and Optical Physics, vol. 74. https://doi.org/10.1103/PhysRevA.74.012719

Collisional-radiative calculations of He line emission in low-temperature plasmas. / Ballance, C. P.; Griffin, D. C.; Loch, S. D.; Boivin, R. F.; Pindzola, M. S.

Physical Review A - Atomic, Molecular, and Optical Physics. 2006. (Physical Review A - Atomic, Molecular, and Optical Physics; Vol. 74).

Research output: Chapter in Book/Report/Conference proceedingChapter

TY - CHAP

T1 - Collisional-radiative calculations of He line emission in low-temperature plasmas

AU - Ballance, C. P.

AU - Griffin, D. C.

AU - Loch, S. D.

AU - Boivin, R. F.

AU - Pindzola, M. S.

PY - 2006

Y1 - 2006

N2 - We present spectral modeling results for neutral helium. Our underlying atomic data contains radiative transition rates that are generated from atomic structure calculations and electron-impact excitation rates, that are determined from both the standard R-matrix method and the R-matrix with pseudostates RMPS method. In this paper, we focus on transitions of particular importance to diagnostic line ratios. For example, our calculated rate coefficient for the electron-impact transition 1s3s 1S→1s3p 1P, which has a pronounced effect on the 728.1 nm diagnostic spectral line, is found to be in good agreement with previous experimental mea- surements. We also consider transitions from the 1s2 1S ground and 1s2s 3S terms to terms of the n=4 shell. They are found to be affected significantly by coupling of the bound states to the target continuum continuum coupling, which is included in our RMPS calculation, but not in our standard R-matrix calculation. We perform collisional-radiative calculations to determine spectral line intensity ratios for three ratios of particular interest, namely the 504.8 nm/471.3 nm, 492.2 nm/471.3 nm, and 492.2 nm/504.8 nm line ratios. Comparing our results determined from the RMPS excitation rates with those from the standard R-matrix excitation rates, we find that continuum coupling affects the rate coefficients significantly, leading to different values for all three line ratios. We also compare our modeling results with spectral measurements taken recently on the Auburn Helicon plasma device, finding that the ground and metastable populations are not in equilibrium, and that the experimental measurements are more consistent with the 1s2s 3S metastable term populations being short lived in the plasma.

AB - We present spectral modeling results for neutral helium. Our underlying atomic data contains radiative transition rates that are generated from atomic structure calculations and electron-impact excitation rates, that are determined from both the standard R-matrix method and the R-matrix with pseudostates RMPS method. In this paper, we focus on transitions of particular importance to diagnostic line ratios. For example, our calculated rate coefficient for the electron-impact transition 1s3s 1S→1s3p 1P, which has a pronounced effect on the 728.1 nm diagnostic spectral line, is found to be in good agreement with previous experimental mea- surements. We also consider transitions from the 1s2 1S ground and 1s2s 3S terms to terms of the n=4 shell. They are found to be affected significantly by coupling of the bound states to the target continuum continuum coupling, which is included in our RMPS calculation, but not in our standard R-matrix calculation. We perform collisional-radiative calculations to determine spectral line intensity ratios for three ratios of particular interest, namely the 504.8 nm/471.3 nm, 492.2 nm/471.3 nm, and 492.2 nm/504.8 nm line ratios. Comparing our results determined from the RMPS excitation rates with those from the standard R-matrix excitation rates, we find that continuum coupling affects the rate coefficients significantly, leading to different values for all three line ratios. We also compare our modeling results with spectral measurements taken recently on the Auburn Helicon plasma device, finding that the ground and metastable populations are not in equilibrium, and that the experimental measurements are more consistent with the 1s2s 3S metastable term populations being short lived in the plasma.

U2 - 10.1103/PhysRevA.74.012719

DO - 10.1103/PhysRevA.74.012719

M3 - Chapter

SN - 1050-2947\n1094-1622

T3 - Physical Review A - Atomic, Molecular, and Optical Physics

BT - Physical Review A - Atomic, Molecular, and Optical Physics

ER -

Ballance CP, Griffin DC, Loch SD, Boivin RF, Pindzola MS. Collisional-radiative calculations of He line emission in low-temperature plasmas. In Physical Review A - Atomic, Molecular, and Optical Physics. 2006. (Physical Review A - Atomic, Molecular, and Optical Physics). https://doi.org/10.1103/PhysRevA.74.012719