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Abstract We report new branching fraction (BF) measurements for 156 ultraviolet and optical transitions of Gdii. These transitions range in wavelength (wavenumber) from 2574 to 6766 Å (38,838–14,777 cm−1) and originate in one odd-parity and 11 even-parity upper levels. Nine of the 12 levels, accounting for 126 of the 156 transitions, are studied for the first time. BFs are determined for three levels studied previously for the purpose of comparison. The levels studied for the first time are high lying, ranging in energy from 36,845 to 40,774 cm−1. The BFs are determined from emission spectra from two different high-resolution spectrometers. These are combined with radiative lifetimes reported in an earlier study to produce a set of transition probabilities and log(gf) values with accuracy ranging from 5% to 30%. Comparison is made to experimental and theoretical transition probabilities from the literature where such data exist. Abundances derived from these new log(gf) values for 21 Gdiilines in two metal-poor stars yield results consistent with previous studies, and they demonstrate that the new log(gf) values can be used in stellar abundance analysis as a self-consistent extension of previous work.
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Energy Levels of Singly Ionized and Neutral Hafnium
Abstract Improved energy levels for singly ionized and neutral hafnium of both even and odd parity are determined from Fourier transform spectrometer data using a least-squares optimization procedure. Data from interferometric spectrometers provide much tighter control of systematic uncertainties of line position measurements than can be achieved using dispersive spectrometers. The strong optical and near-UV lines connecting these levels are most likely to be used in the determination of isotopic abundance patterns. Comparisons of new results to published ones strongly suggest that our energy levels have systematic uncertainties in the mK (1 mK = 0.001 cm−1) range or smaller, and that widely used tables of energy levels for ionized Hf have systematic errors of approximately 70 mK.
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- Award ID(s):
- 1814512
- PAR ID:
- 10361744
- Publisher / Repository:
- DOI PREFIX: 10.3847
- Date Published:
- Journal Name:
- The Astrophysical Journal Supplement Series
- Volume:
- 258
- Issue:
- 2
- ISSN:
- 0067-0049
- Format(s):
- Medium: X Size: Article No. 27
- Size(s):
- Article No. 27
- Sponsoring Org:
- National Science Foundation
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