Atomic data from the IRON Project

Abstract

Collision strengths for electron induced transitions in the beryllium-like ion Fe +22 are calculated using the intermediate coupling frame transformation (ICFT) version of the R-matrix programs. Our target has 98 fine structure states 1s 2 nl n l S LJ corresponding to n = 2 and n = 2, 3, 4. The present calculation is for electron impact energies in the range 3.15 to 380 Ry. When T exceeds about ten million degrees one needs to take account of contributions to the thermally averaged collision strength Υ coming from electrons with energies in excess of 380 Ry. We discuss a way of allowing for these contributions. Values of Υ for all the transitions between the ground state and the excited states 1s 2 2l n l n l S L J , with n = 2, 3, 4 are tabulated as a function of log T. The temperature range 6.3 ≤ log T ≤ 8.1 is centred on log T = 7.1 which is approximately where Fe +22 has maximum abundance in ionization equilibrium. To the best of our knowledge these are the first R-matrix calculations for Fe +22 for excitations to the n = 3, 4 levels. Good agreement with previous distored-wave calculations is found. However, the resonance contributions have an important effect on the effective collision strengths and in turn on the level populations.

Spectral diagnostics with the SDO EVE flare lines

“…The main atomic data for this ion are from Chidichimo et al (2005). The Fe xxiii 132.906 Å resonance line is blended with the Fe xx 132.84 Å transition, the strongest line from Fe xx.…”

Recommended data on proton-ion collision rate coefficients for Fe X–Fe XXIII ions

“…27 the temperature dependencies of the proton excitation rates calculated in the papers of Feldman et al (1980), Doyle (1987), and Ryans et al (1998) are shown together with the data of Chidichimo et al (2005) for electron excitation rates. It is seen that proton collisions are very important for the transitions 2s2p 3 P 0 − 3 P 2 , 2s2p 3 P 1 − 3 P 2 at T > 10 7 K and are insignificant for the transition 2s2p 3 P 0 − 3 P 1 at practically all reasonable temperatures.…”

“…Collision rate coefficients for the transition 2s2p 3 P 0 − 3 P 2 (triangles), 2s2p 3 P 1 − 3 P 2 (opened squares), 2s2p 3 P 0 − 3 P 1 (filled squares) in Be-like Fe XXIII: solid thick line -Eq. (3) for protons, solid thin line -electrons (Chidichimo et al 2005), and thick dashed lines -data of Doyle (1987). necessary to take the proton excitation processes into account in both low and high density plasma.…”

SYSTEMATIC CALCULATIONS OF ENERGY LEVELS AND TRANSITION RATES OF BE-LIKE IONS WITH Z = 10–30 USING A COMBINED CONFIGURATION INTERACTION AND MANY-BODY PERTURBATION THEORY APPROACH

“…Some calculations were performed for selected individual ions (Kramida & Träbert 1995;Tully & Chidichimo 2001Chidichimo et al 2003;Aggarwal et al 2005;Chidichimo et al 2005;Landi & Gu 2006;Savukov & Markhotok 2006;Bhatia & Landi 2007a, 2007bGu 2007;Duan et al 2008;Del Zanna et al 2008;, 2009a, 2009bHudson 2009;Mania et al 2009;Aggarwal & Keenan 2014). However, a majority of these calculations are at the level of a relatively simple configuration interaction method, which implies a relatively lower accuracy.…”