Calculated oscillator strengths for the strongest lines of cosmochronological interest in the visible spectrum of singly ionized uranium (U II)

Gamrath, Sébastien; Palmeri, P.; Quinet, Pascal

doi:10.1093/mnras/sty2194

Cited by 7 publications

(7 citation statements)

References 24 publications

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“…In this work, we test this method, which practically is realized by fitting parameters in Equation (7) to match theoretical lifetimes, Equation (8).…”

Section: Lifetime Of J = 15 and 25 Odd Statesmentioning

confidence: 99%

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CI-MBPT and Intensity-Based Lifetime Calculations for Th II

Savukov

2020

Atoms

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Lifetime calculations of Th II J = 1.5 and 2.5 odd states are performed with configuration–interaction many-body perturbation theory (CI-MBPT). For many J = 2.5 states, lifetimes are quite accurate, but two pairs of J = 2.5 odd states and many groups of J = 1.5 states are strongly mixed, making theoretical predictions unreliable. To solve this problem, a method based on intensities is used. To relate experimental intensities to lifetimes, two parameters, one an overall coefficient of proportionality for transition rates and one temperature of the Boltzmann distribution of populations, are introduced and fitted to minimize the deviation between theoretical and intensity-derived lifetimes. For strongly mixed groups of states, the averaged lifetimes obtained from averaged transition rates were used instead of individual lifetimes in the fit. Close agreement is obtained. Then intensity branching ratios are used to extract individual lifetimes for the strongly mixed states. The resulting lifetimes are compared to available directly measured lifetimes and reasonable agreement is found, considering limited accuracy of intensity measurements. The method of intensity-based lifetime calculations with fit to theoretical lifetimes is quite general and can be applied to many complex atoms where strong mixing between multiple states exists.

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“…In this work, we test this method, which practically is realized by fitting parameters in Equation (7) to match theoretical lifetimes, Equation (8).…”

Section: Lifetime Of J = 15 and 25 Odd Statesmentioning

confidence: 99%

“…These oscillator strengths are considered to be most accurate. Oscillator strength calculations of Th II were performed very recently using pseudorelativistic Hartree-Fock with core polarization (HFR-CPOL) method by Gamrath et al [7], which previously showed promising results for strong U II lines [8].…”

Section: Introductionmentioning

confidence: 99%

CI-MBPT and Intensity-Based Lifetime Calculations for Th II

Savukov

2020

Atoms

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“…Roederer et al (2018b) derived a Th abundance from 5 optical lines (Nilsson et al 2002b) and a U upper limit from 2 optical lines (Nilsson et al 2002a). We perform a new check for the strongest U ii lines listed in the study by Gamrath et al (2018a), and none are detected or useful for further constraining the U abundance. Our recommended Th and U abundances are taken from Roederer et al…”

Section: A24 Ruthenium (Ru Z = 44)mentioning

confidence: 99%

The R-Process Alliance: A Nearly Complete R-Process Abundance Template Derived from Ultraviolet Spectroscopy of the R-Process-Enhanced Metal-Poor Star HD 222925

Roederer,

Lawler,

Hartog

et al. 2022

Preprint

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We present a nearly complete rapid neutron-capture process (r-process) chemical inventory of the metal-poor ([Fe/H] = −1.46 ± 0.10) r-process-enhanced ([Eu/Fe] = +1.32 ± 0.08) halo star HD 222925. This abundance set is the most complete for any object beyond the solar system, with a total of 63 metals detected and seven with upper limits. It comprises 42 elements from 31 ≤ Z ≤ 90, including elements rarely detected in r-process-enhanced stars, such as Ga, Ge, As, Se, Cd, In, Sn, Sb, Te, W, Re, Os, Ir, Pt, and Au. We derive these abundances from an analysis of 404 absorption lines in ultraviolet spectra collected using the Space Telescope Imaging Spectrograph on the Hubble Space Telescope and previously analyzed optical spectra. A series of appendices discusses the atomic data and quality of fits for these lines. The r-process elements from Ba to Pb, including all elements at the third r-process peak, exhibit remarkable agreement with the Solar r-process residuals, with a standard deviation of the differences of only 0.08 dex (17%). In contrast, deviations among the lighter elements from Ga to Te span nearly 1.4 dex, and they show distinct trends from Ga to Se, Nb through Cd, and In through Te. The r-process contribution to Ga, Ge, and As is small, and Se is the lightest element whose production is dominated by the r-process. The lanthanide fraction, log X La = −1.39±0.09, is typical for r-processenhanced stars and higher than that of the kilonova from the GW170817 neutron-star merger event. We advocate adopting this pattern as an alternative to the Solar r-process-element residuals when confronting future theoretical models of heavy-element nucleosynthesis with observations.

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“…It was found that this ab initio method can reproduce well energies and g-factors, but the method is computationally challenging [7] and had limited success in neutral uranium, as we found in our preliminary calculations. While Cowan's code [9] based parametric calculations are able to reproduce energies quite well, they do not give accurate wavefunctions, and, to improve the wavefunctions and transition data accuracy, polarization potentials were introduced to achieve reasonable agreement with experiment: in La II [10] and U II [11] for strong lines. In case of La II, it can be seen that better accuracy is achieved using the CI-MBPT approach with a relatively small number of adjustable parameters to scale the second-order MBPT to improve the accuracy of valence-core interactions [12].…”

Section: Introductionmentioning

confidence: 99%

Configuration–Interaction Perturbation Theory Calculations of Pu II

Savukov

2020

Atoms

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Configuration–interaction perturbation theory (CI–PT) is applied to calculations of low-energy states of Pu II. This ion is quite challenging due to a large number of possible determinants arising from seven valence electrons and strong relativistic effects. The CI–PT calculations agree with experiments for the energies and g-factors for many low-energy states that allowed positive identification of the theoretical levels. Isotope shifts were also used to aid in identification, and, in case of the odd states, fitting with three independent parameters was used to match theoretical isotope shifts to the experimental values with good accuracy. The CI–PT approach tested here on the Pu II ion can be generally used to calculate properties of many complex atoms, including U I that can find application in fundamental and applied science.

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Calculated oscillator strengths for the strongest lines of cosmochronological interest in the visible spectrum of singly ionized uranium (U II)

Cited by 7 publications

References 24 publications

CI-MBPT and Intensity-Based Lifetime Calculations for Th II

CI-MBPT and Intensity-Based Lifetime Calculations for Th II

The R-Process Alliance: A Nearly Complete R-Process Abundance Template Derived from Ultraviolet Spectroscopy of the R-Process-Enhanced Metal-Poor Star HD 222925

Configuration–Interaction Perturbation Theory Calculations of Pu II

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