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

Wang, K.; Jönsson, P.; Ekman, J.; Gaigalas, G.; Godefroid, M. R.; Si, R.; Chen, Z. B.; Li, S.; Chen, C. Y.; Yan, J.

Employing two state-of-the-art methods, multiconfiguration Dirac–Hartree–Fock and second-order many-body perturbation theory, the excitation energies and lifetimes for the lowest 200 states of the 2{s}22{p}4, 2s2{p}5, 2{p}6, 2{s}22{p}33s, 2{s}22{p}33p, 2{s}22{p}33d, 2s2{p}43s, 2s2{p}43p, and 2s2{p}43d configurations, and multipole (electric dipole (E1), magnetic dipole (M1), and electric quadrupole (E2)) transition rates, line strengths, and oscillator strengths among these states are calculated for each O-like ion, from Cr xvii to Zn xxiii. Our two data sets are compared with the National Institute of Standards and Technology and CHIANTI compiled values, and previous calculations. The data are accurate enough for identification and deblending of new emission lines from the Sun and other astrophysical sources. The amount of high-accuracy data is significantly increased for the n = 3 states of several O-like ions of astrophysical interest, where experimental data are very scarce.


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New Fe i Level Energies and Line Identifications from Stellar Spectra. II. Initial Results from New Ultraviolet Spectra of Metal-poor Stars

Peterson, Ruth C.; Kurucz, Robert L.; Ayres, Thomas R.

The Fe i spectrum is critical to many areas of astrophysics, yet many of the high-lying levels remain uncharacterized. To remedy this deficiency, Peterson & Kurucz identified Fe i lines in archival ultraviolet and optical spectra of metal-poor stars, whose warm temperatures favor moderate Fe i excitation. Sixty-five new levels were recovered, with 1500 detectable lines, including several bound levels in the ionization continuum of Fe i. Here, we extend the previous work by identifying 59 additional levels, with 1400 detectable lines, by incorporating new high-resolution UV spectra of warm metal-poor stars recently obtained by the Hubble Space Telescope Imaging Spectrograph. We provide gf values for these transitions, both computed as well as adjusted to fit the stellar spectra. We also expand our spectral calculations to the infrared, confirming three levels by matching high-quality spectra of the Sun and two cool stars in the H-band. The predicted gf values suggest that an additional 3700 Fe i lines should be detectable in existing solar infrared spectra. Extending the empirical line identification work to the infrared would help confirm additional Fe i levels, as would new high-resolution UV spectra of metal-poor turnoff stars below 1900 Å.


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Radiative data for highly excited 3d84d levels in Ni II from laboratory measurements and atomic calculations

Hartman, H.; Engström, L.; Lundberg, H.; Nilsson, H.; Quinet, P.; Fivet, V.; Palmeri, P.; Malcheva, G.; Blagoev, K.

Aims: This work reports new experimental radiative lifetimes and calculated oscillator strengths for transitions from 3d84d levels of astrophysical interest in singly ionized nickel.
Methods: Radiative lifetimes of seven high-lying levels of even parity in Ni II (98 400-100 600 cm-1) have been measured using the time-resolved laser-induced fluorescence method. Two-step photon excitation of ions produced by laser ablation has been utilized to populate the levels. Theoretical calculations of the radiative lifetimes of the measured levels and transition probabilities from these levels are reported. The calculations have been performed using a pseudo-relativistic Hartree-Fock method, taking into account core polarization effects.
Results: A new set of transition probabilities and oscillator strengths has been deduced for 477 Ni II transitions of astrophysical interest in the spectral range 194-520 nm depopulating even parity 3d84d levels. The new calculated gf-values are, on the average, about 20% higher than a previous calculation and yield lifetimes within 5% of the experimental values.


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A study on missing lines in the synthetic solar spectrum near the Ca triplet

Kitamura, Jessica R.; Martins, Lucimara P.; Coelho, Paula

Synthetic stellar spectra are extensively used for many different applications in astronomy, from stellar studies (such as in the determination of atmospheric parameters of observed stellar spectra), to extragalactic studies (e.g. as one of the main ingredients of stellar population models). One of the main ingredients of synthetic spectral libraries are the atomic and molecular line lists, which contain the data required to model all the absorption lines that should appear in these spectra. Although currently available line lists contain millions of lines, a relatively small fraction of these lines have accurate derived or measured transition parameters. As a consequence, many of these lines contain errors in the electronic transition parameters that can reach up to 200%. Furthermore, even for the Sun, our closest and most studied star, state-of-the-art synthetic spectra does not reproduce all the observed lines, indicating transitions that are missing in the line lists of the computed synthetic spectra. Given the importance and wide range of applications of these models, improvement of their quality is urgently necessary. In this work we catalogued missing lines in the atomic and molecular line lists used for the calculation of the synthetic spectra in the region of Gaia, comparing a solar model computed via a recent line list with a high quality solar atlas available in the literature. After that, we attempted the calibration of their atomic parameters with the code ALLiCE; the calibrated line parameters are publicly available for use.


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Line Identification of Atomic and Ionic Spectra of Holmium in the Near-UV

Part I. Spectrum of Ho I

Al-Labady, N.; Özdalgiç, B.; Er, A.; Güzelçimen, F.; Öztürk, I. K.; Kröger, S.; Kruzins, A.; Tamanis, M.; Ferber, R.; Başar, Gö.

The Fourier Transform spectra of a Holmium hollow cathode discharge lamp have been investigated in the UV spectral range from 25,000 up to 31,530 cm‑1 (317 to 400 nm). Two Ho spectra have been measured with neon and argon as buffer gases. Based on the intensity ratios from these two spectra, a distinction was made between atomic and ionic lines (ionic lines are discussed in an accompanying paper). Using the known Ho i energy levels, 71 lines could be classified as transitions of atomic Ho, 34 of which have not been published previously. Another 32 lines, which could not be classified, are listed in the literature and assigned as atomic Ho. An additional 370 spectral lines have been assigned to atomic Ho based on the signal-to-noise ratio in the two spectra measured under different discharge conditions, namely with buffer gases argon and neon, respectively. These 370 lines have not been previously listed in the literature.


Part II. Spectra of Ho II and Ho III

Başar, Gö.; Al-Labady, N.; Özdalgiç, B.; Güzelçimen, F.; Er, A.; Öztürk, I. K.; Ak, T.; Bİlİr, S.; Tamanis, M.; Ferber, R.; Kröger, S.

Fourier Transform spectra of holmium (Ho) in the UV spectral range from 31,530 to 25,000 cm‑1 (317 to 400 nm) have been investigated, particularly focusing on the ionic lines. The distinction between the different degrees of ionization (I, II, and III) is based on differences in signal-to-noise ratios from two Ho spectra, which have been measured with different buffer gases, i.e., neon and argon. Based on 106 known Ho ii and 126 known Ho iii energy levels, 97 lines could be classified as transitions of singly ionized Ho and 9 lines could be classified as transitions of doubly ionized Ho. Of the 97 Ho ii lines, 6 have not been listed in the extant literature. Another 215 lines have been assigned to Ho ii, though they could not be classified on the basis of the known energy levels.


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Fe XVII Opacity at Solar Interior Conditions

Iglesias, Carlos A.; Hansen, Stephanie B.

A recent study of Fe xvii R-matrix calculations aimed at resolving outstanding opacity problems claimed that substantial photon absorption from atomic core ionization processes was not previously considered. It is shown, however, that major opacity models already include cross-sections that are equivalent to the enhancements reported by the R-matrix method. Furthermore, the R-matrix calculations neglected important cross-sections that help to explain why the resultant opacity is lower than other models in the spectral range measured in transmission experiments relevant to the solar interior.


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Extended Calculations with Spectroscopic Accuracy: Energy Levels and Transition Properties for the Fluorine-like Isoelectronic Sequence with Z = 24-30

Si, R.; Li, S.; Guo, X. L.; Chen, Z. B.; Brage, T.; Jönsson, P.; Wang, K.; Yan, J.; Chen, C. Y.; Zou, Y. M.

We have performed extensive multiconfiguration Dirac-Hartree-Fock calculations and second-order many-body perturbation calculations for F-like ions with Z = 24-30. Energy levels and transition rates for electric dipole (E1), electric-quadrupole (E2), electric-octupole (E3), magnetic dipole (M1), and magnetic-quadrupole (M2) transitions, as well as radiative lifetimes, are provided for the lowest 200 levels belonging to the 1{s}22{s}22{p}5, 1{s}22s2{p}6, 1{s}22{s}22{p}43l, 1{s}22s2{p}53l, 1{s}22{p}63l, and 1{s}22{s}22{p}44l configurations of each ion. The results from the two sets of calculations are in excellent agreement. Extensive comparisons are also made with other theoretical results and observed data from the CHIANTI and NIST databases. The present energies and wavelengths are believed to be accurate enough to aid line identifications involving the n = 3 and n = 4 configurations, for which observations are largely missing. The calculated wavelengths and transition data will be useful in the modeling and diagnostics of astrophysical and fusion plasmas.

Article -> http://esoads.eso.org/abs/2016ApJS..227…16S

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