Inner-shell photoexcitation of Fe xv and Fe xvi (original) (raw)
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The Astrophysical Journal Supplement Series, 2002
Fifty-four fine-structure energy levels of Fe x belonging to the configurations 3s 2 3p 5 , 3s3p 6 , 3s 2 3p 4 3d, and 3s3p 5 3d are calculated using extensive configuration-interaction (CI) wave functions, with relativistic effects incorporated through the Breit-Pauli Hamiltonian. The crucial correlation effects arising from the twoelectron excitation configurations 3s 2 3p 3 3d 2 and 3s3p 4 3d 2 are included in the CI expansion. Oscillator strengths and radiative rates are presented for the 460 allowed and intercombination transitions among the 54 levels. The lifetime for the 3s3p 6 2 S 1=2 level is also calculated and compared with available results.
K-shell photoionization and electron impact excitation of Fe�XVII?Fe�XXIII
Astronomy and Astrophysics, 2004
Photoabsorption cross sections across the K edge of Fe -Fe and electron impact K-shell excitation effective collision strengths in Fe -Fe have been computed with the Breit-Pauli R-matrix method. The target models are represented with all the fine-structure levels within the n = 2 complex, built up from single-electron orbital bases obtained in a Thomas-Fermi-Dirac statistical model potential. The effects of radiation and spectator Auger dampings are taken into account by means of an optical potential. In photoabsorption, these effects cause the resonances converging to the K thresholds to display symmetric profiles of constant width that smear the edge, with important implications in spectral analysis. In collisional excitation, they attenuate resonances making their contributions to the effective collision strength practically negligible.
A comprehensive set of UV and x-ray radiative transition rates for Fe XVI
Physica Scripta, 2009
Sodium-like Fe XVI is observed in collisionally ionized plasmas such as stellar coronae and coronal line regions of active galactic nuclei including black hole-accretion disc environments. Given its recombination edge from neon-like Fe XVII at ∼25 Å, the Fe XVI bound-bound transitions lie in the soft x-ray and EUV (extreme ultraviolet) range. We present a comprehensive set of theoretical transition rates for radiative dipole allowed E1 transitions including fine structure for levels with n (S L J ) 10, 9 using the relativistic Breit-Pauli R-matrix (BPRM) method. In addition, forbidden transitions of electric quadrupole (E2), electric octupole (E3), magnetic dipole (M1) and magnetic quadrupole (M2) type are presented for levels up to 5g(SLJ) from relativistic atomic structure calculations in the Breit-Pauli approximation using code SUPERSTRUCTURE. Some of the computed levels are autoionizing, and oscillator strengths among those are also provided. BPRM results have been benchmarked with the relativistic coupled cluster method and the atomic structure Dirac-Fock code GRASP. Levels computed with the electron collision BPRM codes in bound state mode were identified with a procedure based on the analysis of quantum defects and asymptotic wavefunctions. The total number of Fe XVI levels considered is 96, with 822 E1 transitions. Tabulated values are presented for the oscillator strengths f , line strengths S and Einstein radiative decay rates A. This extensive dataset should enable spectral modelings up to highly excited levels, including recombination-cascade matrices.
Photoionization and recombination of Fe XIX
Monthly Notices of the Royal Astronomical Society, 2000
Photoionization cross-sections and recombination rate coefficients are presented for the L-shell ground-state fine-structure levels 2s 2 2p 4 3 P 2,0,1 of Fe xix. Several sets of calculations including relativistic effects are carried out: (i) Breit±Pauli R-matrix (BPRM), (ii) relativistic distorted-wave (RDW), and (iii) a semirelativistic calculation. Non-relativistic LS-coupling calculations are also performed for comparison. The BPRM calculations employ a configuration-interaction target representation for Fe xx consisting of 12 LS terms (23 fine-structure levels), as in the recently reported BPRM calculations by Donnelly et al. The background cross-sections in all three sets of present calculations agree with one another, but differ considerably from those of Donnelly et al. Owing to much more extensive resonance structures in the present BPRM calculations, the sum of the corresponding recombination rate coefficients for the 3 P 2,0,1 levels is up to 50 per cent higher than the LS rates at low temperatures but comparable for higher temperatures; this is in contrast to the results of Donnelly et al. who obtained the LS rates to be higher than their BPRM results by about a factor of 2. Reasons for these discrepancies are discussed.
Photoionization of Fe V around the 3p→ 3d core excitation region
The photoionization cross sections of Fe V are revised in the light of recent experimental measurements. It is found that in order to calculate accurate cross sections through the close-coupling method one must account for three important effects: (1) one-electron orbitals used to represent the target ion must be optimized based on not only the target itself, but also the states of the ionizing system. This is important in order to get the right positions of 3p → 3d states with respect to the ionization threshold.
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.
Photoionization cross sections and dipole transition probabilities for the astrophysically important iron ion Fe IV are presented. The computations were carried out in the close coupling approximation using the R-matrix method including 31 LS terms with multiplicity (2S + 1) = 3 and 5 of the target ion Fe V. All quartets and sextet bound states of Fe IV with n ≤ 10 and L ≤ 8 are considered. The results include 746 LS bound states, dipole oscillator strengths for 34 635 LS transitions, and, for all bound states, detailed photoionization cross sections with extensive resonance structures. These data differ significantly in many cases from the earlier data calculated under the Opacity Project and other theoretical calculations. In particular, the new cross section for the 6 S ground state of Fe IV exhibits a large resonance near the threshold that is not present in previous calculations and is likely to affect the effective photoionization rate significantly. The autoionizing state that corresponds to that resonance as well as the Rydberg series to which it belongs are identified through supplementary close coupling calculations.
Physical Review A, 1999
Relativistic and resonance effects in the photoionization of Mg-like Fe XV are investigated using the Breit-Pauli R-matrix Method (BPRM) at near-threshold and intermediate energies, complemented by the Relativistic Random Phase Approximation (RRPA) and multi-channel quantum defect theory in the energy region up to the L-shell ionization thresholds. The cross sections exhibit extensive resonance structures that considerably enhance the effective photoionization of Fe XV. These results should be of general interest in photoionization modeling of X-ray sources observed by space observatories.
Photoionization cross sections and dipole transition probabilities for the astrophysically important iron ion Fe IV are presented. The computations were carried out in the close coupling approximation using the R-matrix method including 31 LS terms with multiplicity (2S + 1) = 3 and 5 of the target ion Fe V. All quartets and sextet bound states of Fe IV with n ≤ 10 and L ≤ 8 are considered. The results include 746 LS bound states, dipole oscillator strengths for 34 635 LS transitions, and, for all bound states, detailed photoionization cross sections with extensive resonance structures. These data differ significantly in many cases from the earlier data calculated under the Opacity Project and other theoretical calculations. In particular, the new cross section for the 6 S ground state of Fe IV exhibits a large resonance near the threshold that is not present in previous calculations and is likely to affect the effective photoionization rate significantly. The autoionizing state that corresponds to that resonance as well as the Rydberg series to which it belongs are identified through supplementary close coupling calculations.
Inner-shell photodetachment from Fe^{-}
Physical Review A, 2010
Inner-shell photodetachment from Fe − was studied in the 48-to 72-eV photon energy range using a merged ion-photon-beam technique. The absolute photodetachment cross sections of Fe − , leading to Fe + and Fe 2+ ion production, were measured. The 3p → (3d + εd) photoexcitation in Fe − negative ions gives rise to shape resonances. In the near-threshold region, shape-resonance profiles with l = 2 accurately fit the single-photodetachment cross section. Simultaneous double photodetachment was also observed, resulting in an increased Fe 2+ production which obeys a Wannier law. Despite the large number of possible terms resulting from the Fe − 3d open shell, a rough calculation using the R-matrix method qualitatively agrees well with the experimental data.