Precision measurement of relative oscillator strengths - IV. Attainment of 0.5 per cent accuracy. Fe I transitions from levels a5 D0-4 (0.00-0.12 eV)

Abstract

The accuracy of the Oxford method of comparing oscillator strengths has been improved by a factor of 10 to 0.5 per cent (0.002 dex) for low excitation lines. The improvements made to the apparatus are briefly described and its new performance discussed. A test for LTE in the furnace is also described. Relative oscillator strengths for 60 lines of Fe I with excitation potentials between 0.00 and 0.12 eV are given. Those with λ > 320 nm have an accuracy of 0.5 per cent, and those with λ < 320 nm have an accuracy of 1.0 per cent. Absolute values with an accuracy of 2.5 per cent for all lines are given assuming that log gf (371.99 nm) = −0.43 ± 0.01 (2 per cent).