Oscillator Strengths and Electron Collision Rates for Fine‐Structure Transitions in O
                    <scp>ii</scp>

Tayal, S. S.

doi:10.1086/513107

Cited by 65 publications

(57 citation statements)

References 26 publications

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“…Wavelengths of the transitions were measured by Edlen [11], Erikson [12], and Pettersson and Wenaker [13]. The present A values agree well with the published results by Tayal [3] and Natarajan [8], and very well with those of Bell et al [6], some of which were renormalized later by Wiese et al [7]. The correlation interaction between P states are known to show considerable perturbation effect on the states.…”

Section: Allowed E1 Transitionssupporting

confidence: 90%

“…These processes for O II have been studied by many researchers and, in a previous study, we computed collision strengths of O II [1,2] using the Breit-Pauli R-matrix (BPRM) method. Later Tayal [3] presented similar results considering a larger number of collisional excitations. He also presented the radiative transitions among those levels obtained from atomic structure calculations.…”

Section: Introductionmentioning

confidence: 60%

“…Wiese et al [7] carried out an evaluated compilation of results by various authors which is available at the NIST [25] website. Comparisons of present work for transitions from the ground configuration of O II are made with those by Bell et al [6] obtained using the CIV3 code, by Tayal [3] obtained from atomic structure calculations using the multi-configuration Hartree-Fock method, by Natarajan [8] obtained using multi-configuration Dirac-Fock approximation, and by Lennon and Burke [4] in the R-matrix method but in nonrelativistic LS coupling approximation. Experimental measurements correspond mainly to 3s -3p, 3p -3d, and 3d -4f transitions.…”

Section: Allowed E1 Transitionsmentioning

confidence: 80%

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Oscillator strengths and transition probabilities of O II

Nahar

2010

Atomic Data and Nuclear Data Tables

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The abundance of singly ionized oxygen, O II, in planetary nebulae provides crucial diagnostic tests for the physical conditions present in these astrophysical environments. The abundance can be determined from the absorption lines formed by the radiative processes, such as the photo-excitations reported here. Radiative transitions are obtained from a total of 708 fine structure levels of O II with n ≤ 10, l ≤ 9, and 1/2 ≤ J ≤ 17/2. For spectral analysis oscillator strengths, line strengths, and transition probabilities (A) are presented for 51,733 electric dipole fine structure radiative transitions. The calculations were carried out in the relativistic Breit-Pauli R-matrix approximation. The transitions have been identified spectroscopically using quantum defect analysis and other criteria. The calculated energies agree with the observed energies within 5% for most of the levels. However, some relatively large differences are noted, the largest difference being 13% for the level 2s

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Section: Allowed E1 Transitionssupporting

confidence: 90%

Section: Introductionmentioning

confidence: 60%

Section: Allowed E1 Transitionsmentioning

confidence: 80%

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Oscillator strengths and transition probabilities of O II

Nahar

2010

Atomic Data and Nuclear Data Tables

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“…These physical conditions were used to determine the ionic abundances of the elements with available lines. The atomic data used are listed in Stasińska (2005), with the exception of the emissivity of the He i 5876 line, taken from Porter et al (2007), and the collision strenghts for [O ii] lines, taken from Tayal (2007). The emissivities of collisionally excited lines were computed with a 5-level atom approximation, within the code ABELION, written by Stasińska. We assumed that the electron density is uniform in the nebulae and equal to the one given by the [S ii] ratio.…”

Section: 3mentioning

confidence: 99%

The chemical composition of planetary nebulae and HII regions in NGC 3109

Peña¹,

Stasińska²,

Richer³

2007

A&A

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Aims. We present deep spectrophotometry for a sample of 8 planetary nebulae (PNe) and 12 HII regions distributed throughout the dwarf irregular galaxy NGC 3109, in order to analyze the chemical composition of both types of nebulae. Methods. We describe the observations and data reduction, and present line intensities for the nebular emission lines detected. The physical conditions and the abundances of He, O, Ne, N, S and Ar are derived, using the classical T e -based method. We confirm our previous identification of PNe and HII regions based on photometry, except for one object, which we argue is a compact HII region rather than a planetary nebula. Results. We find that the chemical composition of the interstellar medium in NGC 3109, as sampled by its HII regions, is remarkably uniform. The oxygen abundance is log O/H + 12 = 7.77 ± 0.07 in this galaxy, as compared to 8.05 ± 0.09 for the Small Magellanic Cloud (for which we rederived the metallicity in a homogeneous way). PNe show significantly higher oxygen abundances in NGC 3109: log O/H + 12 = 8.16 ± 0.19. Similarly to what has been suggested for some of the PNe in the Magellanic Clouds and other metal-poor galaxies, we argue that oxygen in the PNe in NGC 3109 is affected by dredge up in their progenitors. This could also be the case for neon, although the uncertainties for this element are bigger. Conclusions. From our analysis, we conclude that oxygen and neon are not always a safe indicator of the chemical composition of the interstellar medium at low metallicities. An alternative to the O and Ne enrichment in PNe is that the low metallicity in HII regions has been caused by dilution of the interstellar medium due to an interaction with a neighboring galaxy about a Gyr ago. The excitation patterns of the PNe in NGC 3109 are very different from the excitation patterns of PNe in other galaxies. This issue needs to be investigated further, as it implies that the evolution of PNe depends upon the properties of their progenitor stellar populations, which vary from galaxy to galaxy. This should affect the planetary nebula luminosity function and its use as a distance indicator. Regarding individual objects, we find that the planetary nebula named PN 14 shows clear Wolf-Rayet features, very low excitation and high density. Thus, it is similar to some of the galactic PNe ionized by late [WC] stars.

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“…New collision strengths and transition probabilities are presented by Chen, Qing & Li (2007) and Tayal (2007) For temperature measurements, the most important diagnostics are provided by the [O iii] and [N ii] nebular to auroral line ratios. In a detailed study of the thermal structure of the most metal-poor blue compact galaxy I Zw 18, Péquignot (2008) compares collision strengths of [O iii] published in the literature.…”

Section: Collisional Excited Lines (Cels)mentioning

confidence: 99%

Atomic processes in planetary nebulae

Liu¹

2011

Proc. IAU

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Abstract. Progress in the study of the atomic processes in planetary nebulae (PNe) is reviewed, focusing on the literature published since the last IAU symposium on PNe five years ago. High quality photoionization cross sections and recombination coefficients are now available for the first six ions of the trans-iron elements selenium and krypton, enabling robust modeling of their ionization structure and consequently converting the measured ionic abundances to elemental abundances. Major progress has been achieved in utilizing the recombination spectra of helium and heavy element ions to probe the nebular physical conditions. New ab initio, densitydependent effective recombination coefficients have been calculated for the recombination spectra of O ii and N ii, down to very low temperatures (∼ 100-300 K). Plasma diagnostics based entirely on those heavy element recombination lines are developed and applied to the observations. It is shown that these heavy element recombination lines originate predominately from cold plasmas of temperatures ∼ 1, 000 K, in agreement with the predictions of the bi-abundance model that has been proposed to explain the dichotomy of nebular plasma diagnostics and abundance determinations using collisional excited lines (CELs) on the one hand and optical recombination lines (ORLs) on the other.

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Oscillator Strengths and Electron Collision Rates for Fine‐Structure Transitions in O ii

Cited by 65 publications

References 26 publications

Oscillator strengths and transition probabilities of O II

Oscillator strengths and transition probabilities of O II

The chemical composition of planetary nebulae and HII regions in NGC 3109

Atomic processes in planetary nebulae

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