Atomic data for neutron-capture elements

Sterling, N. C.; Witthoeft, M. C.

doi:10.1051/0004-6361/201117471

Cited by 22 publications

(36 citation statements)

References 76 publications

(98 reference statements)

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“…In addition, all rate coefficients can be obtained at http://www.pa.msu.edu/astro/ atomicdata/charge_transfer/. In tandem with our concurrent investigations into the photoionization and radiative and dielectronic recombination properties of n-capture elements (e.g., Sterling & Witthoeft 2011;Sterling 2011), these CT rate coefficient determinations will enable the abundances of n-capture elements to be reliably determined in ionized astrophysical nebulae. Such studies bear significant implications for n-capture nucleosynthesis, the structure and internal mixing of evolved stars, and the chemical evolution of trans-iron elements in the Universe.…”

Section: Discussionmentioning

confidence: 99%

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Atomic data for neutron-capture elements

Sterling

Stancil

2011

A&A

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We present total and final-state resolved charge transfer (CT) rate coefficients for low-charge Ge, Se, Br, Kr, Rb, and Xe ions reacting with neutral hydrogen over the temperature range 10 2 -10 6 K. Each of these elements has been detected in ionized astrophysical nebulae, particularly planetary nebulae. CT rate coefficients are a key ingredient for the ionization equilibrium solutions needed to determine total elemental abundances from those of the observed ions. A multi-channel Landau Zener approach was used to compute rate coefficients for projectile ions with charges q = 2-5, and for singly-charged ions the Demkov approximation was utilized. Our results for five-times ionized species are lower limits, due to the incompleteness of level energies in the NIST database. In addition, we computed rate coefficients for charge transfer ionization reactions between the neutral species of the above six elements and ionized hydrogen. The resulting total and state-resolved CT rate coefficients are tabulated and available at the CDS. In tandem with our concurrent investigations of other important atomic processes in photoionized nebulae, this work will enable robust investigations of neutron-capture element abundances and nucleosynthesis via nebular spectroscopy.

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Section: Discussionmentioning

confidence: 99%

“…In the first two (Sterling & Witthoeft 2011;Sterling 2011), we furnished multi-configuration Breit-Pauli distorted-wave photoionization cross sections and radiative and dielectronic recombination rate coefficients for Se and Kr ions.…”

Section: Introductionmentioning

confidence: 99%

Atomic data for neutron-capture elements

Sterling

Stancil

2011

A&A

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“…First, a reliable ICF scheme is needed for Xe. This requires photoionization and recombination data such as Sterling &Witthoeft (2011) andSterling (2011) produced for Se and Kr. Secondly, AGB nucleosynthesis model studies are needed to interpret [Xe/Kr] ratios and their relation to the [hs/ls] index used in studies of sprocess nucleosynthesis in AGB stars.…”

Section: S-process Enrichments Of N-capture Elementsmentioning

confidence: 99%

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

García‐Rojas¹,

Madonna²,

Luridiana³

et al. 2015

Mon. Not. R. Astron. Soc.

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The chemical content of the planetary nebula NGC 3918 is investigated through deep, highresolution (R∼40000) UVES at VLT spectrophotometric data. We identify and measure more than 750 emission lines, making ours one of the deepest spectra ever taken for a planetary nebula. Among these lines we detect very faint lines of several neutron-capture elements (Se, Kr, Rb, and Xe), which enable us to compute their chemical abundances with unprecedented accuracy, thus constraining the efficiency of the s-process and convective dredge-up in NGC 3918s progenitor star. We find that Kr is strongly enriched in NGC 3918 and that Se is less enriched than Kr, in agreement with the results of previous papers and with predicted s-process nucleosynthesis. We also find that Xe is not as enriched by the s-process in NGC 3918 as is Kr and, therefore, that neutron exposure is typical of modestly subsolar metallicity AGB stars. A clear correlation is found when representing [Kr/O] vs. log(C/O) for NGC 3918 and other objects with detection of multiple ions of Kr in optical data, confirming that carbon is brought to the surface of AGB stars along with s-processed material during third dredge-up episodes, as predicted by nucleosynthesis models. We also detect numerous refractory element lines (Ca, K, Cr, Mn, Fe, Co, Ni, and Cu) and a large number of metal recombination lines of C, N, O, and Ne. We compute physical conditions from a large number of diagnostics, which are highly consistent among themselves assuming a three-zone ionization scheme. Thanks to the high ionization of NGC 3918 we detect a large number of recombination lines of multiple ionization stages of C, N, O and Ne. The abundances obtained for these elements by using recently-determined state-of-the-art ICF schemes or simply adding ionic abundances are in very good agreement, demonstrating the quality of the recent ICF scheme for high ionization planetary nebulae.

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“…To meet the need, Sterling &Witthoeft (2011) andSterling (2011) have recently presented multi-configuration Breit-Pauli distorted-wave photoionization cross-sections and radiative and di-electronic recombination rate coefficients for the first six ions of the trans-iron elements selenium and krypton, respectively. Charge exchange reaction rate coefficients for low-charge Ge, Se, Br, Kr, Rb and Xe ions reacting with neutral hydrogen are also obtained by Sterling & Stancil (2011) adopting a multi-channel Landau Zener approach.…”

Section: Atomic Processes In Planetary Nebulaementioning

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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Atomic data for neutron-capture elements

Cited by 22 publications

References 76 publications

Atomic data for neutron-capture elements

Atomic data for neutron-capture elements

s-process enrichment in the planetary nebula NGC 3918. Results from deep echelle spectrophotometry

Atomic processes in planetary nebulae

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