Modeling of time-resolved LIBS spectra obtained in Martian atmospheric conditions with a stationary plasma approach

Abstract

In this study, we investigate the characteristics of the LIBS plasma in Martian atmospheric conditions using stationary modeling of the LIBS plasma. LIBS spectra are simulated from a one-dimensional model of the plasma divided into two zones along the line of sight. The simulations are based on local thermal equilibrium and carried out using radiative transfer. The simulated spectra are fitted first to synthetic LIBS spectra to test the implementation and in a second step to time-resolved LIBS data of a carbonate sample obtained in experimentally simulated Martian atmospheric conditions. From the fits to the synthetic LIBS spectra, we confirm that plasmas with spatial gradients in the temperature and densities can be well described in a two-zone plasma model. From the fits to the measured data this observation also holds true. We find that the most of the emission lines are well described in the two-zone model and that the two-zone model is a significant improvement from the one-zone model. Furthermore, we obtain typical values of the plasma properties in the two-zone approximation from 500 ns to 1250 ns after plasma initiation and derive the effect of self-absorption, which is predicted to decrease the strongest pixel intensities by a factor of almost two orders of magnitudes.