Radiative Lifetimes in Nd II and the Solar Neodymium Abundance

Ward, L; Vogel, O.; Ahnesjö, Anders; Arnesen, A.; Hallin, R.; McIntyre, L.C.; Nordling, C.

doi:10.1088/0031-8949/29/6/009

Cited by 15 publications

(10 citation statements)

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“…Transitions are identified by the upper-level energy, angular momentum J , and air wavelength, taken from the earlier references. For stronger transitions (BF > 0.1 or g u A ul > 100 × 10 6 s −1 ), the agreement of gA with other work is excellent, giving an average valueη = −0.12 (16). Table 3 includes comparisons with the data of Den Hartog et al [21], Xu et al [19], and Maier and Whaling [14].…”

Section: Resultsmentioning

confidence: 62%

Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II

Li¹,

Rehse²,

Scholl³

et al. 2007

Can. J. Phys.

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We measured the spontaneous-emission branching fractions of 46 levels in Nd II, selectively populated via single-frequency laser excitation of a 10 keV ion beam. The levels studied had term energies up to 29 955 cm −1 , and decay branches with spontaneous emission in the range 372-850 nm were detected. The experimental accuracy for branching fractions over 0.1 was ∼7%. We used these branching fractions along with our previously determined radiative lifetimes to infer transition probabilities and oscillator strengths for 430 transitions, which are useful for stellar abundance determinations. PACS Nos.: 32.70Cs, 95.30KyRésumé : Nous avons mesuré les rapports de branchement d'émission spontanée de 46 niveaux du Nd II peuplés sélectivement via l'excitation laser monochromatique d'un faisceau d'ions de 10 keV. Les niveaux étudiés ont des termes d'énergie jusqu'à 29 995 cm −1 et nous avons observé des branches de désexcitation spontanée dans le domaine 372-850 nm. La précision expérimentale pour les rapports de branchement au delà de 0.1 était ∼7 %. Nous avons utilisé ces rapports de branchement avec les temps de vie radiatifs déjà déterminés pour en déduire les probabilités de transition et les forces d'oscillateur pour 430 transitions qui sont utiles dans l'étude des abondances stellaires.[Traduit par la Rédaction] present numerous examples of isotopes that may be formed by the r-process, the s-process, the pprocess, or a combination. In comparison to solar abundances, the lanthanides are present in CP stars in great excess; for example, in Przybylski's star (HD 101065), the excess abundance of rare earth elements is 3-4 dex [3]. In CP stars with measurable magnetic-field effects, the spectral lines of the lanthanide elements are among the most enhanced [2]. Several galactic halo stars have recently been discovered with extremely large relative lanthanide abundances. These stars are among the oldest stars in our galaxy, and have the potential to provide much information about nucleosynthesis in novae and supernovae. Lastly, the study of lanthanides in the solar spectrum is experiencing a resurgence of interest with the availability of satellite spectra in the UV and laboratory data from new techniques. Some of the reasons for this interest are the potential contribution of two free electrons by the lanthanides to the solar opacity, the realization that diffusion, which has had a significant fractionating effect on helium [4], may well have affected the heavier elements in the Sun, and increasing caution with regard to the accuracy of meteoritic abundances. Beyond astrophysics, the atomic properties of the lanthanides are needed in the design of commercial high-intensity discharge lamps [5] and in the use of spectra to probe the crystalline structure of divalent and trivalent crystal salts [2].Nd in particular is one of the most abundant rare-earth elements. Overabundance of Nd has been found and studied in many CP stars, for example, the HgMn star HR 7775 [6], the Ap star HD 24712 [7], and the Am star β Aur [8]. As...

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Section: Resultsmentioning

confidence: 62%

Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II

Li¹,

Rehse²,

Scholl³

et al. 2007

Can. J. Phys.

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“…The calculation is repeated, changing the abundance of the element in question, until a match is achieved. The line synthesis code MOOG was Smith et al 1996; (17) Gratton & Sneden 1994;(18) Corliss & Bozman 1962(modified Sneden et al 1996; (19) Ward et al 1984(modified Sneden et al 1996. with the adopted model T eA ¼ 6100 K, log g ¼ 4:2, (Fe) ¼ 6:99, and ¼ 1:4 km s À1 .…”

Section: Abundance Analysismentioning

confidence: 99%

Spectroscopic Verification of Barium Dwarf Candidates: The Analysis of HD 8270, HD 13551, and HD 22589

Pereira¹

2005

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This work presents the abundance patterns of three barium dwarf candidates, HD 8270, HD 13551, and HD 22589, based on high-resolution optical spectra. This work also reports the spectroscopic stellar parameters, temperature, and microturbulent velocity, as well as the stellar surface gravity from a solution of excitation and ionization equilibria of Fe i and Fe ii lines under the assumption of local thermodynamic equilibrium. The abundance analysis reveals that HD 8270, HD 13551, and HD 22589 have metallicities of ½Fe/ H ¼ À0:43, À0.28, and À0.12, respectively. It was found that the abundances of iron group and -elements follow the abundance pattern of a disk population. The heavy-element abundance patterns of the three stars show enhancements by a factor of 4-8 with respect to the Sun. The abundances of the s-process elements are discussed and compared with other barium giants and dwarfs through diagrams involving the indices [hs/ls] and [s/Fe]. The metallicity distribution of barium giants and dwarfs is also discussed.

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“…In order to refine the solar content of Nd, Ward et al (1984, 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.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd ii)

Xu¹,

Svanberg²,

Cowan³

et al. 2003

Monthly Notices of the Royal Astronomical Society

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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.

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Radiative Lifetimes in Nd II and the Solar Neodymium Abundance

Cited by 15 publications

References 10 publications

Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II

Fast-ion-beam laser-induced-fluorescence measurements of branching fractions and oscillator strengths in Nd II

Spectroscopic Verification of Barium Dwarf Candidates: The Analysis of HD 8270, HD 13551, and HD 22589

Theoretical and experimental lifetime and oscillator strength determination in singly ionized neodymium (Nd ii)

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