Oscillator strengths of Cr I lines lying between 200 and 541 nm from hook-method and absorption measurements in a furnace

Abstract

Oscillator strengths of 148 transitions in the neutral chromium atom with wavelengths between 200 and 541 nm were determined in a high-temperature furnace by use of the hook and absorption methods for strong and weak lines, respectively. 114 of these gf -values are reported for the first time. Hook spectra taken at wavelengths near 430 nm assured accurate knowledge of the product of f -value and column density for prominent transitions with lower levels lying at 0 and ≈ 1 eV. The absolute scale is based on the best available oscillator strengths for the 427 nm resonance triplet. The relative scale matches measurements of the relative intensities of emission lines that correspond to transitions from a common upper level (z 5 P 0 2 ) to the ground level (a 7 S 3 ) as well as to excited terms (a 5 S, a 5 D). A slight adjustment (well within the calibration uncertainties) made our oscillator-strength scale agree with gf -values obtained by Cocke, Stark & Evans from beam-foil and branching-ratio measurements. Uncertainty estimates, given for each oscillator strength, are substantiated by the agreement (within error limits) of those f -values that could be measured by both, absorption and hook method.