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. Subject headings: atomic data -quasars: absorption lines -quasars: individual (QSO 2359-1241) -ISM: individual objects (HH 202) -ISM: individual objects (Orion) -ISM: individual objects (ESO-Hα 574, Par-Lup 3-4) -ISM: jets and outflows -ISM: lines and bands -stars: pre-main sequence reliable scattering calculations. For this work we use a combination of numerical methods: the pseudo-relativistic Hartree-Fock (hfr) code of Cowan (1981); the Multiconfiguration Dirac-Fock (mcdf) code (Dyall et al. 1989), and the scaled Thomas-Fermi-Dirac central-field potential as implemented in autostructure (Badnell 1997). hfr calculationshfr uses a superposition of configurations approach to account for configuration interactions. The code solves the Hartree-Fock equations for each electronic configuration.Relativistic corrections are also included in this set of equations. The radial parts of the multi-electron Hamiltonian can be adjusted empirically to reproduce the spectroscopic energy levels in a least-squares fit procedure. These semi-empirical corrections are used to account for the contributions from higher order correlations in the atomic state functions.The following configurations were explicitly included in the physical model: 3d 6 4s, 3d 7 , 3d 5 4s 2 , 3d 6 5s, 3d 6 4d, 3d 6 5d, 3d 5 4p 2 , 3d 5 4d 2 , 3d 5 4s4d, 3s3p 6 3d 7 4s, 3s3p 6 3d 8 , and 3s3p 6 3d 6 4s 2 . This configuration expansion extends the one used in the previous hfr calculation by Quinet et al. (1996) by including 3d 5 4d 2 and 3s3p 6 3d 6 4s 2 . In order to minimize the discrepancies between computed and experimental energy levels, the hfr technique was used in combination with a well-known least-squares optimization of the radial parameters. The fitting procedure was applied to 3d 6 4s, 3d 7 , ...
A detailed investigation of radiative parameters for electric dipole (E1) transitions is presented for the ions Ra II, Ac III, Th IV and U VI along the francium isoelectronic sequence. The pseudo-relativistic Hartree–Fock (HFR) method including core-polarization effects is used for the calculations. Comparisons with multiconfigurational Dirac–Fock (MCDF) calculations show that the most important relativistic effects are taken into account. In view of their importance in nuclear laser spectroscopy, forbidden rates (transitions M1 and E2) in Th IV are also reported in this paper.
This work reports new experimental radiative lifetimes of six 3d 2 ( 3 F)5s levels in singly ionized titanium, with an energy around 63 000 cm −1 and four 3d 2 ( 3 F)4p odd parity levels where we confirm previous investigations. Combining the new 5s lifetimes with branching fractions measured previously by Pickering et al., we report 57 experimental log gf values for transitions from the 5s levels. The lifetime measurements are performed using time-resolved laser-induced fluorescence on ions produced by laser ablation. One-and two-step photon excitation is employed to reach the 4p and 5s levels, respectively. Theoretical calculations of the radiative lifetimes of the measured levels as well as of oscillator strengths for 3336 transitions from these levels are reported. The calculations are carried out by a pseudorelativistic Hartree-Fock method taking into account core-polarization effects. The theoretical results are in a good agreement with the experiments and are needed for accurate abundance determinations in astronomical objects.
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