Accurate Experimental Lifetimes of Excited Levels in Nd II

Ward, L; Vogel, O.; Arnesen, A.; Hallin, R.; Wännström, A.

doi:10.1088/0031-8949/31/3/001

Cited by 49 publications

(44 citation statements)

References 20 publications

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“…The gf values adopted for the observed Nd ii lines are the experimental values from Meggers et al (1975) and Ward et al (1985).…”

Section: Neodymiummentioning

confidence: 99%

“…The neodymium abundance in HR 7775 was determined from a number of unblended and sufficiently strong Nd ii lines, the gf values of which had been determined from three sources: Ward et al 1985;Kurucz 1993a, as determined from lifetimes provided by Ward et al 1985;and Meggers et al 1975, corrected with a factor of 0.62 as given in Kurucz 1993a. In the present study 24 lines were observed and analyzed with synthetic spectra.…”

Section: Neodymium In 32 Aqr and Hr 7775mentioning

confidence: 99%

“…This analysis served to check the consistency of the abundance Blaise et al (1984) b Classifications from Martin et al (1978) References: [1] Meggers et al (1975), corrected with a factor of 0.62 as given in Kurucz (1993a); [2] Ward et al (1985); [3] Kurucz (1993a), as determined from lifetimes provided by Ward et al (1985). determination for HR 7775 and to discern possible blends that could be present in HR 7775, while absent in 32 Aqr.…”

Section: Neodymium In 32 Aqr and Hr 7775mentioning

confidence: 99%

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The presence of Nd and Pr in HgMn stars

Dolk

Wahlgren

Lundberg³

et al. 2002

A&A

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Abstract.Optical region spectra for a number of upper main sequence chemically peculiar (CP) stars have been observed to study singly and doubly ionized praseodymium and neodymium lines. In order to improve existing atomic data of these elements, laboratory measurements have been carried out with the Lund VUV Fourier Transform Spectrometer (FTS). From these measurements wavelengths and hyperfine structure (hfs) have been studied for selected Pr ii, Pr iii and Nd iii lines of astrophysical interest. Radiative lifetimes for some excited states of Pr ii have been determined with the aid of laser spectroscopy at the Lund Laser Center (LLC) and have been combined with branching fractions measured in the laboratory to calculate gf values for some of the stronger optical lines of Pr ii. With the aid of the derived gf values and laboratory measurements of the hfs, a praseodymium abundance was derived from selected Pr ii lines in the spectrum of the Am star 32 Aqr. This abundance was used to derive astrophysical gf values for selected Pr iii lines in 32 Aqr, and these gf values were used to get a praseodymium abundance for the HgMn star HR 7775. The praseodymium abundance in HR 7775 was then utilized to derive astrophysical gf values for all observable Pr iii lines in this star. The neodymium abundance, derived from unblended lines of Nd ii in HR 7775, has been utilized to establish astrophysical gf values for observed Nd iii lines in the optical region of this star. Selected Pr iii and Nd iii lines have been identified and studied in a number of HgMn stars and three hot Am stars. The praseodymium and neodymium abundance change rapidly from an approximate 1-1.2 dex enhancement for the hot Am stars to 1.5-3 dex enhancement for the cool HgMn stars, indicating a well-defined boundary between the hot Am and HgMn stars in the vicinity of 10 500 K. The enhancement of praseodymium and neodymium in Am and HgMn stars may be explained by diffusive processes active in the stellar atmosphere, while the observed discontinuity might be explained by a thin hydrogen convection zone thought to be present for the Am stars, but absent in the HgMn stars. The absence of a convection zone would cause the diffused elements to gather higher in the atmosphere of HgMn stars compared to Am stars, and explain the observed increase in abundance.

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“…The gf values adopted for the observed Nd ii lines are the experimental values from Meggers et al (1975) and Ward et al (1985).…”

Section: Neodymiummentioning

confidence: 99%

Section: Neodymium In 32 Aqr and Hr 7775mentioning

confidence: 99%

Section: Neodymium In 32 Aqr and Hr 7775mentioning

confidence: 99%

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The presence of Nd and Pr in HgMn stars

Dolk

Wahlgren

Lundberg³

et al. 2002

A&A

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“…In order to refine the solar content of Nd, Ward et al (1984Ward et al ( , 1985 measured the lifetimes of eight and 24 levels in Nd II, respectively, using the laser-ion beam technique, and deduced oscillator strengths of some Nd II lines from a combination of the BFs deduced from arc spectra (Corliss & Bozman 1962;Reader et al 1980) or measured by Maier & Whaling (1977) and of the new lifetime values.…”

mentioning

confidence: 99%

Radiative lifetime measurements in Er II by time-resolved laser spectroscopy

Jiang

Zhang

et al. 2003

J. Phys. B: At. Mol. Opt. Phys.

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Radiative lifetime measurements were performed with time-resolved laser-induced fluorescence techniques for 24 levels of Nd II in the energy range 20 500-32 500 cm −1 . For 17 levels, no previous experimental data exist. These results have allowed the testing of new theoretical calculations with the relativistic Hartree-Fock method taking configuration interactions and core-polarization effects into account, and a satisfying agreement has been found for this complex ion. A new set of calculated oscillator strengths, accurate within a few per cent for the strongest transitions, is presented for 107 lines of astrophysical interest appearing in the wavelength range 358.0-1100.0 nm. These results will be useful to evaluate abundance values of neodymium in chemically peculiar stars in relation with cosmochronology.Key words: atomic data -atomic processes -stars: chemically peculiar. I N T RO D U C T I O NThe consideration of the r-process abundance patterns in some stars allows an age determination of the earliest galactic halo. In particular, the comparison of the abundances of the heavy elements (i.e. thorium and uranium) synthesized soon after the formation of our Galaxy with those of lighter stable neutron capture elements allows the estimation of the age of this halo. However, some singly ionized rare-earths, interesting for cosmochronometry (in relation with the third n-capture peak), have only poorly determined transition probabilities (Sneden, Lawler & Cowan 2002). As a consequence, narrowing the uncertainties in age estimates relies clearly on further improvements in r-process theory but also on high-resolution spectroscopy of very metal-poor stars itself depending upon accurate atomic data.The age of some very metal-poor stars (see e.g. Cayrel et al. 2001) can be estimated, by comparison of abundance ratios of radioactive and stable nuclear species, using different pairs of elements such as U/Th, U/Os and U/Ir. Nd II is one of the elements which can be used as a stable nuclear species in cosmochronology for estimating the age of the Galaxy (Lawler, Whaling & Grevesse 1990). The present study is mainly aimed at obtaining a new set of atomic data for this ion having in mind contribution to the cosmochronometry based on the pair U/Nd. E-mail: E.Biemont@ulg.ac.be In a more general context, accurate atomic data for lanthanide ions are required for refining the stellar elemental abundances and for more firmly establishing the odd-even effect observed in many stars: in fact the elements with an even atomic number appear generally more abundant than the odd elements. In some stars, however, this odd-even effect does not appear clearly because some of the lines (which are frequently only a few of them) used for deducing abundance values are affected by blending with the abundant elements (iron-group elements) and by possible unknown hyperfine structure effects.Singly ionized neodymium is frequently observed in astrophysical spectra and the analysis of Nd II lines leads to strong overabundance estimates of th...

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“…However, since the wavelength range between each missing line was large enough, we calibrated them separately, running ALiCCE for each missing line identified. The log gf values obtained from VALD were (Kurucz 2013) (e) (Ward et al 1985) (f) (Wiese et al 1966) (g) (Duquette & Lawler 1982) (h) (Martin et al 1988) (i) (Kurucz 2010) (j) (Corliss & Bozman 1962) (l) (Kurucz & Peytremann 1975) a http://kurucz.harvard.edu/linelists/gfnew/ used as initial guesses. Table 4 shows the values obtained for each line calibrated by ALiCCE.…”

Section: Line Calibrationmentioning

confidence: 99%

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

Kitamura¹,

Martins²,

Coelho³

2017

A&A

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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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Accurate Experimental Lifetimes of Excited Levels in Nd II

Abstract: channel time time NO on off Accurate Experimental Lifetimes of Excited Levels in Nd II counts counts counts Counts Ion on off on o f f current

Cited by 49 publications

References 20 publications

The presence of Nd and Pr in HgMn stars

The presence of Nd and Pr in HgMn stars

Radiative lifetime measurements in Er II by time-resolved laser spectroscopy

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

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