R-matrix electron-impact excitation data for the Be-like iso-electronic sequence

Fernández-Menchero, L. and Del Zanna, G. and Badnell, N.R. (2014) R-matrix electron-impact excitation data for the Be-like iso-electronic sequence. Astronomy and Astrophysics, 566. A104. ISSN 0004-6361 (https://doi.org/10.1051/0004-6361/201423864)

[thumbnail of Fernandez-menchero-etal-AA-2015-R-matrix-electron-impact-excitation-data]
PDF. Filename: Fernandez_menchero_etal_AA_2015_R_matrix_electron_impact_excitation_data.pdf
Accepted Author Manuscript

Download (764kB)| Preview


Aims. Emission lines from ions in the Be-like isoelectronic sequence can be used for reliable diagnostics of temperature and density of astrophysical and fusion plasmas over a wide range of temperatures. Surprisingly, interpolated data is all that is available for a number of astrophysically important ions. Methods. We have carried out intermediate coupling frame transformation R-matrix calculations which include a total of 238 fine-structure levels in both the configuration interaction target and close-coupling collision expansions. These arise from the configurations 1s2 2 {s, p} nl with n = 3−7, and l = 0−4 for n ≤ 5 and l = 0−2 for n = 6,7. Results. We obtain ordinary collision strengths and Maxwell-averaged effective collision strengths for the electron-impact excitation of all the ions of the Be-like sequence, from B+ to Zn26+. We compare with previous R-matrix calculations and interpolated values for some benchmark ions. We find good agreement for transitions n = 2−2 with previous R-matrix calculations but some disagreements with interpolated values. We also find good agreement for the most intense transitions n = 2−3 which contribute via cascade to the (n = 2) diagnostic radiating levels.