A Photospheric Solar Iron Abundance from Weak Fe II Lines

Abstract

The main difficulties encountered in determining a photospheric solar iron abundance are considered and a way is shown to circumvent most of them. Branching fractions of weak Fe II lines are measured from a hollow-cathode discharge to derive accurate transition probabilities from a previously determined lifetime. These transition probabilities — together with accurate equivalent widths from the solar spectrum — are subsequently used to calculate a photospheric iron abundance. The choice of suitable lines results in an abundance value nearly independent of any assumption concerning the temperature model and line-broadening parameters.