Electron impact excitation of Fe XVI: radiative and excitation rates

Abstract

Aims. In this paper we report calculations for energy levels, radiative rates, collision strengths, and effective collision strengths for transitions in Fe XVI. Methods. For energy levels and radiative rates we have used the General purpose Relativistic Atomic Structure Package (grasp), and for the compuations of collision strengths the Dirac Atomic R-matrix Code (darc) has been adopted. Results. Energies for the lowest 39 levels among the n ≤ 7 ( ≤ 4) configurations of Fe XVI are reported. Additionally, radiative rates, oscillator strengths, and line strengths are reported for all electric dipole (E1), magnetic dipole (M1), electric quadrupole (E2), and magnetic quadrupole (M2) transitions among these levels. Electron impact excitation collision strengths have also been calculated for all 741 transitions among the above 39 levels over a wide energy range up to 220 Ryd. Resonances have been resolved in the threshold region, and effective collision strengths have been obtained over a wide temperature range up to 10 7 K. Comparisons are made with the available results in the literature, and the accuracy of the present results is assessed.

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

“…However, the data of Younis et al (2007) show a large scatter. Sampson et al (1990), KON98 to Kimura et al (1998), and AK06 to Aggarwal & Keenan (2006), for Fe 15+ . NIST compiled data are given for lower charge ions.…”

“…2a. The data of Aggarwal & Keenan (2006) Kimura et al (1998) reported the g f -values between LS terms. We partition statistically -such an assumption is a good one at low nuclear charge.…”

“…For Al 2+ , the present results agree to within 20% when compared with those available from Hudson & Bell (2005) and NIST's v.3 compilation. For Fe 15+ , a complete set of data from Aggarwal & Keenan (2006) is available and so more transitions are compared. They show that the present g f -values agree to within 20% for most transitions.…”

“…Thereafter, more elaborate calculations have been performed for several ions. For example, Eissner et al (1999) presented Breit-Pauli R-matrix results for electron-impact excitations amongst the 12 fine-structure levels of the n ≤ 4 configurations of Fe 15+ ; Hudson & Bell (2005) reported R-matrix results for level-resolved excitations among the lowest 17 finestructure levels belonging to 3l, 4l, 5s, 5p and 5d configurations of Al 2+ by re-coupling LS-coupling results via the jajom code; Aggarwal & Keenan (2006) reported results for level-resolved excitations among the lowest 39 levels amongst the n ≤ 7 (l ≤ 4) configurations of Fe 15+ by using the Dirac atomic R-matrix code darc.…”

Benchmarking atomic data for astrophysics: a first look at the soft X-ray lines

“…Sampson et al (1990) performed relativistic DW calculations for this ion, and the data are available within CHIANTI. Cornille et al (1997) Aggarwal & Keenan (2006) perfomed a calculation with the Dirac Atomic R-matrix Code (DARC). These data were used by Keenan et al (2007) to show that reasonable agreement for the A85 data was present, although they did not discuss the temperature sensitivity of these lines.…”