Improved Wavelengths and Oscillator Strengths of Doubly Ionized Iron Group Elements

Details Improved Wavelengths and Oscillator Strengths of Doubly Ionized Iron Group Elements Improved Wavelengths and Oscillator Strengths of Doubly Ionized Iron Group Elements

May 2007

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007aas...210.8807s&link_type=abstract

American Astronomical Society Meeting 210, #88.07; Bulletin of the American Astronomical Society, Vol. 39, p.201

Astronomy and Astrophysics

Astrophysics

Scientific paper

Improvements in the resolution, accuracy, and range of astrophysical spectra obtained by state-of-the-art space-and ground-based spectrographs have highlighted the need for corresponding improvements in the atomic data. Transition wavelengths with uncertainties of 1 part in 10^7 and oscillator strengths with uncertainties of 10 to 15% are needed to accurately interpret modern astrophysical spectra.
The spectra of hot (B-type) stars are dominated by the doubly ionized spectra of the iron group elements. We present new measurements of Cr III, Fe III, and Co III made with a Fourier transform spectrometer (FTS) and a Penning discharge source. The FTS at Imperial College [J. C. Pickering, Vibrational Spectrosc., 29, pp.27-43 (2002)] covers a spectral range from the visible to the VUV (down to 140 nm) with a typical wavenumber uncertainty of a few parts in 10^8. Additional measurements were carried out at the US National Institute of Standards & Technology using their FTS and the Normal Incidence Vacuum (grating) Spectrograph (NIVS). The NIVS spectra were recorded beyond the FTS wavelength cut-off using phosphor image plates, which have the advantage over conventional photographic plates of a linear intensity response over a wide dynamic range, thus allowing branching ratios, and hence oscillator strengths, to be determined.
Intensity- and wavelength-calibrated line lists have been produced, and term analyses are underway. Measured lines are, in many cases, an order of magnitude more accurate than previous measurements and the energy level uncertainty established is typically improved by a factor or 3 more. Work is also underway to establish new measured oscillator strengths for Fe III.
This work is supported in part by NASA Grant NAG5-12,668, NASA inter-agency agreement W-10,255, PPARC, the Royal Society of the UK, and by the Leverhulme Trust.

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