Astronomy and Astrophysics – Astronomy
Scientific paper
Feb 1996
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1996mnras.278..997b&link_type=abstract
Monthly Notices of the Royal Astronomical Society, Volume 278, Issue 4, pp. 997-1004.
Astronomy and Astrophysics
Astronomy
27
Atomic Data, Line: Formation, Stars: Abundances
Scientific paper
Oscillator strengths and transitional probabilities for LaII are computed using a Hartree-plus-statistical-exchange-interaction approximation to the standard Hartree-Fock procedure. Relativistic and electron correlation corrections are included, and configuration interactions involving all reliably established LaII electron configurations are considered. Leading eigenvector percentages for the 5d6d and 5d7s configurations are reported here for the first time. Criteria are developed and applied for selecting the more reliable calculated oscillator strengths. A set of 70 such values is used to calibrate Monograph 145 intensities to produce moderately accurate gf-values. Comparison of an initial two-parameter fit to an equation of the form log(gf)-log(I_145lambda^3)=c _1+c_2E_upper (for E_upper in cm^-1) with beam-laser lifetime measurements shows the resulting log(gf) values to be systematically too large by about 0.26. The reason for this discrepancy is note entirely understood, but it is likely to be due at least in part to the incomplete treatment of core polarization effects in our calculations. Modification of the original calibration in the light of the experimental lifetime data yields the following recommended values for the fitting parameters: c_1=-16.503 and c_2=7.752x10^-5. Log(gf) values computed for LaII lines using this calibration of the Monograph 145 intensities should be accurate to about +/-0.20 dex over the energy range 0 to ~70000 cm^-1. The predictions of this formula are in good agreement with published astrophysical log(gf) values for 34 LaII features in the solar spectrum longward of ~4300A, and yield a mean difference (and standard deviation) of -0.07+/-0.30.
Barisciano P. Jr. L.
Bord Donald J.
Cowley Ch. R.
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