Lifetime calculations in Yb II

Biémont, Émile; Dutrieux, J. F.; Martı́n, I.; Quinet, Pascal

doi:10.1088/0953-4075/31/15/006

Cited by 96 publications

(54 citation statements)

References 34 publications

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“…In the present paper, we report lifetime measurements of two 4f 13 6p energy levels in Yb III together with a comprehensive calculation performed using the relativistic Hartree-Fock (HFR) method taking both intravalence correlation and core-polarization effects into account. This paper extends lifetime measurements and calculations in Yb ions previously reported by Biémont et al (1998), Li et al (1999) and Wyart et al (2001).…”

Section: Introductionsupporting

confidence: 87%

Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII

Biémont¹,

Garnir²,

Li³

et al. 2001

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

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The analysis of the spectrum of Yb III has been extended allowing us to establish 11 new energy level values. In addition, radiative lifetimes of two excited states of Yb III have been measured for the first time using time-resolved laserinduced fluorescence following two-photon excitation. The good agreement between experimental results and semi-empirical calculations performed with the relativistic Hartree-Fock method including core-polarization effects allows the determination of transition probabilities for 15 lines.

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Section: Introductionsupporting

confidence: 87%

Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII

Biémont¹,

Garnir²,

Li³

et al. 2001

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

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“…They have renormalised theoretical oscillator strengths from Biémont et al (1998) using lifetimes from Pinnington et al (1997). The isotopic and hyperfine splitting data are taken from Mårtensson-Pendril et al (1994), and the solar isotopic ratios from Anders & Grevesse (1989) have been assumed.…”

Section: Continuedmentioning

confidence: 99%

The Hamburg/ESO R-process enhanced star survey (HERES)

Jonsell¹,

Barklem²,

Gustafsson³

et al. 2006

A&A

168

277

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We have derived abundances of 33 elements and upper limits for 6 additional elements for the metal-poor ([Fe/H] = −2.42) turn-off star HE 0338−3945 from high-quality VLT-UVES spectra. The star is heavily enriched, by about a factor of 100 relative to iron and the Sun, in the heavy s-elements (Ba, La, ...). It is also heavily enriched in Eu, which is generally considered an r-element, and in other similar elements. It is less enriched, by about a factor of 10, in the lighter s-elements (Sr, Y and Zr). C is also strongly enhanced and, to a somewhat lesser degree, N and O. These abundance estimates are subject to severe uncertainties due to NLTE and thermal inhomogeneities which are not taken into detailed consideration. However, an interesting result, which is most probably robust in spite of these uncertainties, emerges: the abundances derived for this star are very similar to those of other stars with an overall enhancement of all elements beyond the iron peak. We have defined criteria for this class of stars, r + s stars, and discuss nine different scenarios to explain their origin. None of these explanations is found to be entirely convincing. The most plausible hypotheses involve a binary system in which the primary component goes through its giant branch and asymptotic giant branch phases and produces CNO and s-elements which are dumped onto the observed star. Whether the r-element Eu is produced by supernovae before the star was formed (perhaps triggering the formation of a low-mass binary), by a companion as it explodes as a supernova (possibly triggered by mass transfer), or whether it is possibly produced in a high-neutron-density version of the s-process is still unclear. Several suggestions are made on how to clarify this situation.Key words. stars: population ii -stars: fundamental parameters -stars: abundances -Galaxy: halo -Galaxy: abundances -Galaxy: evolution IntroductionElements with atomic numbers Z > 30 are believed to be almost exclusively synthesized in neutron-capture (n-capture) reactions. In the most metal-poor stars the overall abundance of these elements varies from star to star, by more than a factor of 100 at a given metallicity (McWilliam et al. 1995;Ryan et al. 1996). Also, the different abundance ratios vary, e.g. the Ba/Eu ratio tends to decline with decreasing [Fe/H]

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“…Fortunately, most neutron-capture element species considered here have been subjected to extensive laboratory investigations within the past two decades (Biémont et al 1998;Den Hartog et al 2003, 2006Ivarsson et al 2001Ivarsson et al , 2003Lawler et al 2001aLawler et al ,b,c, 2004Lawler et al , 2006Lawler et al , 2007Lawler et al , 2008Lawler et al , 2009Ljung et al 2006;Nilsson et al 2002;Wickliffe et al 2000;Xu et al 2006). We employed g f −values determined by these laboratory efforts.…”

Section: Line Selection and Atomic Datamentioning

confidence: 99%

The Hamburg/ESOR-process enhanced star survey (HERES)

Mashonkina

Christlieb

Barklem

et al. 2010

A&A

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AstrophysicsThe Hamburg/ESO R-process enhanced star survey (HERES) V ABSTRACTAims. We present a detailed abundance analysis of a strongly r-process enhanced giant star discovered in the HERES project, HE 2327−5642, for which [Fe/H] = −2.78, [r/Fe] = +0.99. Methods. We determined the stellar parameters and element abundances by analyzing the high-quality VLT/UVES spectra. The surface gravity was calculated from the non-local thermodynamic equilibrium (NLTE) ionization balance between Fe i and Fe ii, and Ca i and Ca ii.Results. Accurate abundances for a total of 40 elements and for 23 neutron-capture elements beyond Sr and up to Th were determined in HE 2327−5642. For every chemical species, the dispersion in the single line measurements around the mean does not exceed 0.11 dex. The heavy element abundance pattern of HE 2327−5642 is in excellent agreement with those previously derived for other strongly r-process enhanced stars, such as CS 22892-052, CS 31082-001, and HE 1219-0312. Elements in the range from Ba to Hf match the scaled Solar r-process pattern very well. No firm conclusion can be drawn about the relationship between the fisrt neutroncapture peak elements, Sr to Pd, in HE 2327−5642 and the Solar r-process, due to the uncertainty in the Solar r-process. A clear distinction in Sr/Eu abundance ratios was found between the halo stars of different europium enhancement. The strongly r-process enhanced stars contain a low Sr/Eu abundance ratio at [Sr/Eu] = −0.92 ± 0.13, while the stars with 0 < [Eu/Fe] < 1 and [Eu/Fe] < 0 have 0.36 dex and 0.93 dex higher Sr/Eu values, respectively. Radioactive dating for HE 2327−5642 with the observed thorium and rare-earth element abundance pairs results in an average age of 13.3 Gyr, when based on the high-entropy wind calculations, and 5.9 Gyr, when using the Solar r-residuals. We propose that HE 2327−5642 is a radial-velocity variable based on our high-resolution spectra covering ∼4.3 years.

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Lifetime calculations in Yb II

Cited by 96 publications

References 34 publications

Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII

Experimental and theoretical energy levels, transition probabilities and radiative lifetimes in YbIII

The Hamburg/ESO R-process enhanced star survey (HERES)

The Hamburg/ESOR-process enhanced star survey (HERES)

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