A radiation-damped R -matrix approach to the electron-impact excitation of helium-like ions for diagnostic application to fusion and astrophysical plasmas


Autoria(s): Whiteford, A D; Badnell, N R; Ballance, C. P.; O'Mullane, M G; Summers, H P; Thomas, A L
Data(s)

2001

Resumo

Electron-impact excitation collision strengths for transitions between all singly excited levels up to the n = 4 shell of helium-Eke argon and the n = 4 and 5 shells of helium-like iron have been calculated using a radiation-damped R-matrix approach. The theoretical collision strengths have been examined and associated with their infinite-energy limit values to allow the preparation of Maxwell-averaged effective collision strengths. These are conservatively considered to be accurate to within 20% at all temperatures, 3 x 10(5)-3 x 10(8) K forAr(16+) and 10(6)-10(9) K for Fe24+. They have been compared with the results of previous studies, where possible, and we find a broad accord. The corresponding rate coefficients are required for use in the calculation of derived, collisional-radiative, effective emission coefficients for helium-like lines for diagnostic application to fusion and astrophysical plasmas. The uncertainties in the fundamental collision data have been used to provide a critical assessment of the expected resultant uncertainties in such derived data, including redistributive and cascade collisional-radiative effects. The consequential uncertainties in the parts of the effective emission coefficients driven by excitation from the ground levels for the key w, x, y and z lines vary between 5% and 10%. Our results remove an uncertainty in the reaction rates of a key class of atomic processes governing the spectral emission of helium-like ions in plasmas.

Identificador

http://pure.qub.ac.uk/portal/en/publications/a-radiationdamped-r-matrix-approach-to-the-electronimpact-excitation-of-heliumlike-ions-for-diagnostic-application-to-fusion-and-astrophysical-plasmas(70fcea20-4832-4cb1-a8be-5caa549f20cf).html

http://dx.doi.org/10.1088/0953-4075/34/15/320

Idioma(s)

eng

Direitos

info:eu-repo/semantics/restrictedAccess

Fonte

Whiteford , A D , Badnell , N R , Ballance , C P , O'Mullane , M G , Summers , H P & Thomas , A L 2001 , ' A radiation-damped R -matrix approach to the electron-impact excitation of helium-like ions for diagnostic application to fusion and astrophysical plasmas ' Journal of Physics B: Atomic, Molecular and Optical Physics , vol 34 , no. 15 , pp. 3179-3191 . DOI: 10.1088/0953-4075/34/15/320

Tipo

article