Transition Probabilities and Their Accuracy

Huber, M. C. E.; Sandeman, R. J.

doi:10.1088/0031-8949/22/4/009

Cited by 25 publications

(15 citation statements)

References 83 publications

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“…Fuhr et al (1988) give the highest priority to two sets of experimental transition probabilities for Ni i presented by Huber & Sandeman (1980) and by Doerr & Kock (1985). In the mean time, two new sets of experimental measurements were published.…”

Section: Iron Group Elementsmentioning

confidence: 99%

VALD–2: Progress of the Vienna Atomic Line Data Base

Kupka¹,

Piskunov²,

Ryabchikova³

et al. 1999

Astron. Astrophys. Suppl. Ser.

1,509

1,435

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Abstract. We describe the updated version of the "Vienna Atomic Line Data Base" (VALD, Piskunov et al. 1995) which represents a considerable improvement over the first installation from 1994. The original line lists have been complemented with critically evaluated data obtained from experimental measurements and theoretical calculations which are necessary for computing state-ofthe-art line opacities in stellar atmospheres, as well as for synthesizing spectra for high precision analyses. In this paper, we present new and improved data sets for neutral species and ions of Si, P, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Ru, Xe, La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, Re, Pt, Au, Hg, and Pb. For some species data are available in VALD for the first time. We explain our choice of quality rankings by reviewing the literature for the new data and by comparison with source lists included into VALD. For some cases, we produced new line data by weighted averaging of data from different sources with individual error estimates in order to increase the reliability of VALD line lists.Software modifications allow remote users of VALD to specify individual extraction parameters as an alternative to the default settings of the VALD team and to have direct control over the quality ranking of line data. A World-Wide-Web interface is described which provides easy access to all new features.To simplify proper crediting of all authors of atomic data, VALD now includes a compilation of all publications used in each type of reply.Finally, we briefly discuss the future roadmap of VALD developments, including the incorporation of molecular transitions and integration with external data bases.Send offprint requests to: F. Kupka

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Section: Iron Group Elementsmentioning

confidence: 99%

VALD–2: Progress of the Vienna Atomic Line Data Base

Kupka¹,

Piskunov²,

Ryabchikova³

et al. 1999

Astron. Astrophys. Suppl. Ser.

1,509

1,435

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“…Nickel Four lines of Ni I are employed. For 3 lines we employed the oscillator strengths from Blackwell et al (1989); for the remaining line we used the f -value from Huber & Sandeman (1980).…”

Section: Scandiummentioning

confidence: 99%

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

Barklem¹,

Christlieb

Beers

et al. 2005

A&A

506

760

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Abstract. We present the results of analysis of "snapshot" spectra of 253 metal-poor halo stars −3.8 ≤ [Fe/H] ≤ −1.5 obtained in the HERES survey. The snapshot spectra have been obtained with VLT/UVES and have typically S /N ∼ 54 per pixel (ranging from 17 to 308), R ∼ 20 000, λ = 3760-4980 Å. This sample represents the major part of the complete HERES sample of 373 stars; however, the CH strong content of the sample is not dealt with here. The spectra are analysed using an automated line profile analysis method based on the Spectroscopy Made Easy (SME) codes of Valenti & Piskunov. Elemental abundances of moderate precision (absolute rms errors of order 0.25 dex, relative rms errors of order 0.15 dex) have been obtained for 22 elements, C, Mg, Al, Ca, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Zn, Sr, Y, Zr, Ba, La, Ce, Nd, Sm, and Eu, where detectable. Of these elements, 14 are usually detectable at the 3σ confidence level for our typical spectra. The remainder can be detected in the least metal-poor stars of the sample, spectra with higher than average S /N, or when the abundance is enhanced. Among the sample of 253 stars, disregarding four previously known comparison stars, we find 8 r-II stars and 35 r-I stars. The r-II stars, including the two previously known examples CS 22892-052 and CS 31082-001, are centred on a metallicity of [Fe/H] = −2.81, with a very small scatter, on the order of 0.16 dex. The r-I stars are found across practically the entire metallicity range of our sample. We also find three stars with strong enhancements of Eu which are s-process rich. A significant number of new very metal-poor stars are confirmed: 49 stars with [Fe/H] < −3 and 181 stars with −3 < [Fe/H] < −2. We find one star with [Fe/H] < −3.5. We find the scatter in the abundance ratios of Mg, Ca, Sc, Ti, Cr, Fe, Co, and Ni, with respect to Fe and Mg, to be similar to the estimated relative errors and thus the cosmic scatter to be small, perhaps even non-existent. The elements C, Sr, Y, Ba and Eu, and perhaps Zr, show scatter at [Fe/H] < ∼ −2.5 significantly larger than can be explained from the errors in the analysis, implying scatter which is cosmic in origin. Significant scatter is observed in abundance ratios between light and heavy neutron-capture elements at low metallicity and low levels of r-process enrichment.

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“…In this case the density of this level factors out of equation ( 5 . 3 ~) and the ratio of unknown to known ,f-values is then a function of frequency only (Huber and Sandeman 1980b). Because frequencies may be determined with high precision, the potential accuracy of the method is very high.…”

Section: It)mentioning

confidence: 99%

“…The tunable laser has been used to accurately measure oscillator strengths and lifetimes by exploiting non-linear effects Beigang 1981, andearlier references in Huber andSandeman 1980b) and to improve and extend the classical absorption (see, e.g., Wexler et al , Burgess et a1 1980, Huang and Wang 1981 and dispersion methods (see, e.g., Crance et a1 1975, Takubo et a1 1975). Furthermore, some of the measurements of parity non-conservation mentioned above use tunable lasers for the classical, but long neglected, magneto-rotation method, which may be perceived as a differential dispersion measurement (see, e.g., Huber and Sandeman 1980b). There is also an increased number of lifetime determinations for levels in neutral atoms that have been made with narrow-bandwidth tunable lasers-including either direct twophoton absorption or two-step excitation via an intermediate level to levels with the same parity as the ground state.…”

Section: Introductionmentioning

confidence: 99%

The measurement of oscillator strengths

1986

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The methods and techniques currently used to measure oscillator strengths (or, equivalently, f-values and transition probabilities) are reviewed. Both linear and non-linear optical methods are discussed.Following references to critical compilations and bibliographies, the definitions concerning the interaction between an electromagnetic radiation field and a medium (consisting of free atoms, for example) are given: linear and non-linear susceptibilities and radiative constants are introduced. Next, the basic principles of linear methods (dispersion, absorption and emission) and non-linear methods (interaction effects near and off resonance) are explained.Measurement techniques are described in detail. The subjects covered are as follows: introductory remarks on equilibrium, number densities, and relative and absolute oscillator-strength scales; methods based on anomalous dispersion (hook and fringe-shift methods, further interferometric techniques and magneto-rotation); methods based on emission and absorption (the curve of growth, absorption methods yielding absolute and relative $values, and emission methods). We introduce the designation 'Ladenburg method' for a combined method that permits oscillator strengths to be determined without assumptions on plasma state. Subsequently, we discuss the methods based on non-linear interactions (phase-matching in non-linear wave mixing, stimulated Raman scattering, dynamic Stark effect) as well as further methods involving lasers.We emphasise the progress toward more accurate measurements in quantitative spectroscopy and the concomitant new applications. We also point out areas where technological advances concerning light sources, spectrometers and standards, open new opportunities for further, more refined studies in experimental and theoretical atomic and molecular physics.

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Transition Probabilities and Their Accuracy

Cited by 25 publications

References 83 publications

VALD–2: Progress of the Vienna Atomic Line Data Base

VALD–2: Progress of the Vienna Atomic Line Data Base

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

The measurement of oscillator strengths

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