Atomic data for opacity calculations: XX. Photoionization cross sections and oscillator strengths for Fe II

Abstract

Abstract. Large scale ab initio calculations for the radiative data of Fe II have been carried out in the close coupling (cc) approbation employing the it-matrix method and a target state expansion consisting of 83 LS terms of Fe III. All bound states of Fe II with n ≤ 10 and l ≤ 7are considered. The results include 1301 bound states in LS coupling, oscillator strengths for 35 941 transitions among the bound LS states, and detailed photoionization cross sections for all bound states. Autoionizing resonances, as well as the coupling to excited core states, enhance the photoionization cross sections substantially. The calculations of oscillator strengths have been extended beyond the requirement of the Opacity Project to include a large number of fine structure transitions in Fe II, using an algebraic transformation of the LS coupled line strength and the observed energies. The present ƒ-values compare favourably with available experimental values and the calculations by Kurucz. However, the present results differ considerably from earlier 16-state R-matrix calculations and the new radiative data yield Rosseland mean opacities that are 50% higher. Some special features in the monochromatic opacity spectra of Fe II are also noted.

The origin of the anomalous intensity ratio between very bright UV FeII lines and their satellites in gaseous condensations close to the starηCarinae

“…which can be proved by precise calculations similar to those reported in (Nahar & Pradhan 1994) in the range slightly above the ionization limit of FeII. The requirement in Eq.…”

“…According to Johansson & Letokhov (2001b), for the effective temperature of Lyα, T eff (Lyα) 10 000 K, the resonance enhancement of the photoionization cross-section can provide for the depopulation of the lower states at a rate of W 1i ph 1/T 1 . It is most important that the narrow resonances of the photoionization cross-sections of Fe II (Nahar & Pradhan 1994) and the energy difference between the levels c 4 F 7/2 and c 4 F 9/2 (Fig. 4, ∆E = 30 cm −1 ) must provide for the preferable depopulation of the c 4 F 7/2 state (1b) and the resulting weaker absorption of the A and C ultraviolet lines.…”

The FERRUM project: transition probabilities for forbidden lines in [Fe II] and experimental metastable lifetimes

“…Calculations are sensitive to level mixing and performing ab initio calculations which reproduce the mixing properties of the system is not trivial. This is illustrated in Nahar & Pradhan (1994), Nahar (1995), Hibbert & Corrégé (2005), Corrégé & Hibbert (2006) and Pickering et al (2002). In particular, Pickering et al (2002) emphasized that even though the agreement between the theoretical and experimental Fe ii Avalues investigated by Pickering et al (2002) are in general extremely good, probabilities related to spin forbidden transitions that occur due to level mixing may differ by up to an order of magnitude.…”

Net emission coefficients of argon iron plasmas with electron Stark widths scaled to experiments

“…For iron and its ions the photoionization cross sections given in [32,33] and [34] are used. Following the approach of Verner et al [30] the autoionization resonances contained in these cross sections are smoothed using a Gauss profile with a half width at half maximum of 5 nm.…”