How to address self-absorption in LIBS using millisecond time-width detectors

Abstract

To calculate self-absorption in Laser Induced Breakdown Spectroscopy (LIBS) using long-acquisition-time detectors (millisecond-range) it is necessary to account for the evolution of the plasma during the acquisition time and, consequently, the variation in the emitted spectral intensity. This study develops a model that accounts for temperature variations during the measurement period, assuming an adiabatic plasma explosion. By parameterizing all emission and absorption quantities using temperature (T), the model allows for the calculation of spectral line intensities in the presence of self-absorption. The model is applied to binary TiZr alloys, where predictions of pure element spectra are compared with experimental data, and self-absorption is analyzed as stoichiometry varies in six alloys. The model's predictions are validated against experimental curve of growth (C.O.G.) values. Furthermore, this approach provides a method to estimate photon emission probabilities (Einstein coefficients, A_ki).