RADIATIVE L-SHELL TRANSITIONS IN Fe XIX AND Fe XX IONS

Abstract

We compute the wavelengths and oscillator strengths for the 3s, 3d → 2p, and 3p → 2s emission lines in Fe xix and Fe xx ions by using a configuration interaction Dirac-Fock and Dirac-Fock-Sturm method combined with second-order Brillouin-Wigner perturbation theory. We provide a complete list of computed wavelengths and oscillator strengths in both the velocity and length gauge for these transitions, many of which have never previously been reported. A comparison of our data with laboratory measurements and other theoretical predictions allows us to estimate an uncertainty of ∼2 mÅ in the wavelengths and an uncertainty of 2%-3% in the oscillator strengths. We expect that our calculations will provide a means of identifying emission lines from astrophysical sources and improve the ability to detect blending in X-ray grating spectra from Chandra and XMM-Newton. As an example, we present a simulated emission spectrum of Capella and find improved agreement between the observations and our calculations, compared with previous data sets.

Extended Calculations of Spectroscopic Data: Energy Levels, Lifetimes, and Transition Rates for O-like Ions from Cr xvii to Zn xxiii

“…The data sets of the n ≥ 3 states reported by Gu (2005bGu ( , 2007; Kotochigova et al (2007Kotochigova et al ( , 2010 are also of high accuracy. However, Gu (2005bGu ( , 2007 provided energy data for O-like Fe and Ni but not transition rates, and Kotochigova et al (2007Kotochigova et al ( , 2010 only reported transition wavelengths and rates in the range from 12 A to 16Å in Fe XIX.…”

“…Most of them targeted atomic data for low-lying states of the (1s 2 )2s 2 2p 4 , 2s2p 5 , and 2p 6 config-urations (the n = 2 complex) (Baluja & Zeippen 1988a,b;Galavis et al 1997;Vilkas et al 1999;Zhang & Sampson 2002;Gu 2005a;Hu et al 2011;Rynkun et al 2013;Fontes & Zhang 2015). Because of their wide applications for analyzing new observations of astrophysical sources, as well as for modeling and diagnosing a variety of plasmas, energy and transition data for higher-lying states of the n ≥ 3 complexes are also eagerly needed (Phillips et al 1982;Acton et al 1985;Landi & Phillips 2005;Kotochigova et al 2007Kotochigova et al , 2010Raassen & Pollock 2013). Among the studies of the n ≥ 3 states of Fe XIX we mention the calculations of Jonauskas et al (2004) using the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, the calculations of Landi & Gu (2006) using the standard relativistic configuration interaction (RCI) method, the AUTOSTRUCTURE calculations of Butler & Badnell (2008), and the relativistic Breit-Pauli calculations of Nahar (2011).…”

Extended calculations of level and transition properties in the nitrogen isoelectronic sequence: Cr XVIII, Fe XX, Ni XXII, and Zn XXIV

“…A general observation is that the quartets states are energetically lower than the doublet states because electron correlation effects are smaller and converge faster with respect to the orbital set for high spin states than for low spin states Galvez et al 2005). The calculations Kotochigova et al (2010).…”

“…, 30 were covered. Kotochigova et al (2010) evaluated the wavelengths and oscillator strengths for the 2s 2 2p 2 3s, 3d → 2s 2 2p 3 , and 2s2p 3 3p → 2s 2 2p 3 transitions in Fe XX using a configuration interaction Dirac-Fock-Sturm (MDFS) method combined with the second-order Brillouin-Wigner perturbation theory. Bhatia et al (1989) determined transition parameters between n = 2 and n = 3 levels of Ar XII, Ti XVI, Fe XX, Zn XXIV, and Kr XXX using the SUPERSTRUCTURE (SS) code.…”

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

“…A significant improvement in accuracy was achieved in the MBPT calculations compared with the results of the RCI method implemented in the FAC code, for example, uncertainties of wavelengths (Gu 2007) were determined to be a few mÅ through extensive comparison with the measurements of Chen et al (2007). The reliability and accuracy of this method were further confirmed by other elaborate theoretical calculations (Kotochigova et al 2007(Kotochigova et al , 2010Ekman et al 2014;Wang et al 2014) and very recent measurements (Gu et al 2011) in the EUV region. The present work has significantly increased the amount of available data for Be-like ions.…”