Electron Impact Excitation Collision Strengths for Fine-Structure Transitions in of Fe IX (original) (raw)

Electron Impact Excitation Collision Strengths of Transitions in Fe XII

Bulletin of the American Physical Society, 2010

We present Maxwellian-averaged effective collision strengths for the electron-impact excitation of S iii over a wide range of electron temperatures of astrophysical importance, log T e (K) = 3.0-6.0. The calculation incorporates 53 fine-structure levels arising from the six configurations 3s 2 3p 2 , 3s3p 3 , 3s 2 3p3d, 3s 2 3p4s, 3s 2 3p4p and 3s 2 3p4d, giving rise to 1378 individual lines, and is undertaken using the recently developed RMATRX II plus FINE95 suite of codes. A detailed comparison is made with a previous R-matrix calculation and significant differences are found for some transitions. The atomic data are subsequently incorporated into the modeling code cloudy to generate line intensities for a range of plasma parameters, with emphasis on allowed UV and EUV emission lines detected from the Io plasma torus. Electron density-sensitive line ratios are calculated with the present atomic data and compared with those from CHIANTI v7.1, as well as with Io plasma torus spectra obtained by FUSE and EUVE. The present line intensities are found to agree well with the observational results and provide a noticeable improvement upon the values predicted by CHIANTI.

Electron Impact Excitation Collision Strengths for EUV Lines of Fe VII

2013

Electron collisions with Fe-peak elements: Fe IV

Astronomy & Astrophysics, 2006

Electron-impact excitation collision strengths of the Fe-peak element Fe IV are calculated in the close-coupling approximation using the parallel R-matrix program PRMAT. One hundred and eight LS -coupled states arising from the 3d 5 , 3d 4 4s and 3d 4 4p configurations of Fe IV, are retained in the present calculations. Accurate multi-configuration target wavefunctions are employed with the aid of 3p 2 → 3d 2 electron promotions and a 4d correlation orbital. The effective collision strengths required in the analysis of astrophysically important lines in the Fe IV spectra, are obtained by averaging the electron collision strengths for a wide range of incident electron energies, over a Maxwellian distribution of velocities. Results are tabulated for forbidden transitions between the 3d 5 , 3d 4 4s and the 3d 4 4p manifolds for electron temperatures (T e in degrees Kelvin) in the range 3.3 ≤ Log T e ≤ 6.0 that are applicable to many laboratory and astrophysical plasmas. The present results provide new results for forbidden lines in the Fe IV spectrum studied here.

Electron-impact fine-structure excitation of Fe II at low temperature

MNRAS, 2019

Fe II emission lines are observed from nearly all classes of astronomical objects over a wide spectral range from the infrared to the ultraviolet. To meaningfully interpret these lines, reliable atomic data are necessary. In the work presented here we focused on low-lying fine-structure transitions, within the ground term, due to electron impact. We provide effective collision strengths together with estimated uncertainties as functions of temperature of astrophysical importance (10−100 000 K). Due to the importance of fine-structure transitions within the ground term, the focus of this work is on obtaining accurate rate coefficients at the lower end of this temperature range, for applications in low-temperature environments such as the interstellar medium. We performed three different flavours of scattering calculations: (i) an intermediate coupling frame transformation (ICFT) R-matrix method, (ii) a Breit-Pauli R-matrix (BPRM) method, and (iii) a Dirac Atomic R-matrix Code (DARC). The ICFT and BPRM calculations involved three different AUTOSTRUCTURE target models each. The DARC calculation was based on a reliable 20 configuration, 6069 level atomic structure model. Good agreement was found with our BPRM and DARC collision results compared to previous R-matrix calculations. We present a set of recommended effective collision strengths for the low-lying forbidden transitions together with associated uncertainty estimates.

Electron impact excitation of the iron peak element Fe II

Journal of Physics B-atomic Molecular and Optical Physics, 2002

Effective collision strengths for electron-impact excitation of Fe II are presented for all sextet-to-quartet transitions among the 38 L S states formed from the basis configurations 3d 6 4s, 3d 7 and 3d 6 4p. A total of 112 individual transitions are considered at electron temperatures in the range 30-100 000 K, encompassing values of importance for applications in astrophysics as well as laboratory plasmas. A limited comparison is made with earlier theoretical work and large differences are found to occur at the temperatures considered. In particular, it is found that the inclusion or omission of some (N + 1)-bound configurations in the Hamiltonian matrices describing the collision process can have a huge effect on the resulting effective collision strengths, by up to a factor of four in some cases.

Atomic data and spectral model for Fe III

We present new atomic data (radiative transitions rates and collision strengths) from large scale calculations and a non-LTE spectral model for Fe III. This model is in very good agreement with observed astronomical emission spectra, in contrast with previous models that yield large discrepancies with observations. The present atomic computations employ a combination of atomic physics methods, e.g. relativistic Hatree-Fock, the Thomas-Fermi-Dirac potential, and Dirac-Fock computation of A-values and R-matrix with intermediate coupling frame transformation and Dirac R-matrix. We study the advantages and shortcomings of each method. It is found that the Dirac R-matrix collision strengths yield excellent agreement with observations, much improved over previously available models. By contrast, the transformation of LS-coupling R-matrix fails to yield accurate effective collision strengths at around 10 4 K, despite using very large configuration expansions, due to the limited treatment of spin-orbit effects in the near threshold resonances of the collision strengths. The present work demonstrates that accurate atomic data for low ionization iron-peak species is now within reach.

ATOMIC DATA AND SPECTRAL MODEL FOR Fe II

The Astrophysical Journal, 2015

We present extensive calculations of radiative transition rates and electron impact collision strengths for Fe II. The data sets involve 52 levels from the 3d 7 , 3d 6 4s, and 3d 5 4s 2 configurations. Computations of A-values are carried out with a combination of state-of-the-art multiconfiguration approaches, namely the relativistic Hartree-Fock, Thomas-Fermi-Dirac potential, and Dirac-Fock methods; while the R-matrix plus intermediate coupling frame transformation, Breit-Pauli R-matrix and Dirac R-matrix packages are used to obtain collision strengths. We examine the advantages and shortcomings of each of these methods, and estimate rate uncertainties from the resulting data dispersion. We proceed to construct excitation balance spectral models, and compare the predictions from each data set with observed spectra from various astronomical objects. We are thus able to establish benchmarks in the spectral modeling of [Fe II] emission in the IR and optical regions as well as in the UV Fe II absorption spectra. Finally, we provide diagnostic line ratios and line emissivities for emission spectroscopy as well as column densities for absorption spectroscopy. All atomic data and models are available online and through the AtomPy atomic data curation environment.

Fe IX CALCULATIONS FOR THE SOLAR DYNAMICS OBSERVATORY

The Astrophysical Journal, 2011

New calculations of the energy levels, radiative transition rates and collisional excitation rates of Fe ix have been carried out using the Flexible Atomic Code, paying close attention to experimentally identified levels and extending existing calculations to higher energy levels. For lower levels, R-matrix collisional excitation rates from earlier work have been used. Significant emission is predicted by these calculations in the 5f-3d transitions, which will impact analysis of SDO AIA observations using the 94Å filter.

Dirac R-matrix calculation for electron-impact excitation of S xiii

Astronomy & Astrophysics, 2013

Context. Sulfur emission lines in the soft X-ray and extreme-ultraviolet regions are observed in a variety of laboratory and astrophysical spectra. But accurate electron impact excitation data for S xiii for state-of-the-art NLTE spectral models are scarce. Aims. We calculated electron-impact excitation collision strengths and effective collision strengths of S xiii for transitions among the lowest-lying 98 fine-structure states 1s 2 2lnl corresponding to principal quantum numbers n = 2, 3, 4. The effective collision strengths for these transitions were computed over a wide temperature range (log 10 T e (K) = 4.53-7.53) for various astrophysical plasma conditions. Methods. We used the fully-relativistic parallel Dirac R-matrix code to calculate collision strengths. To generate target wavefunctions and energy levels for scattering calculations, we employed the GRASP0 multi-configuration Dirac-Fock code for states up to n = 5. Results. The wavefunctions are generated from 27 configurations-1s 2 2lnl (n = 2, 3, 4, 5)-giving rise to 166 j j energy levels. The collision and effective collision strengths among the lowest 98 fine-structure levels are compared with the previous theoretical calculations. The collision strengths for most transitions agree well at higher incident electron energies. Conclusions. The resonant contributions to effective collision strengths are most dominant at lower temperatures.

Electron Impact Excitation Collision Strengths for Fine-Structure Transitions in of Fe IX (original) (raw)

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