Calculation of relative oscillator strengths of spectral lines from atomic self-absorption data

Abstract

A method is described for calculating the relative absorption oscillator strengths of spectral lines of an element from the gradients of their working curves in emission spectral analysis. A mathematical expression for the gradient of the working curve is derived taking into account the atomic self- absorption of the spectral lines in the cooler region of the discharge and assuming a Doppler broadening line profile for both emission and self-absorption. Local thermal equilibrium is assumed in the absorption region in the arc fringe, and the principle of detailed balance is applied to that region for evaluating the relative population of the lower excited states of the atoms. Correlation between theory and published experimental results for the average gradient of the working curves for 14 lines of Fe I lead to calculation of their relative oscillator strengths as well as to some informations of the average temperatures of the emission and absorption regions. The good agreement between the calculated gf values and those determined by other investigators emphasizes the validity of the assumption of local thermal equilibrium in the arc fringe.