Emission and absorption spectroscopies applied to laser pulse induced plasma analysis

This work has been performed in the purpose of probing solid surfaces by using LIPS (laser induced plasma) technique. The behavior of the produced plasma is very difficult to simulate owing to the shortness of the involved time and space scale. Besides classical emission spectroscopy diagnostics, we have put into operation an original absorption experiment which provides more reliable and numerous information about the plasma temperature and number densities. This study, which couples experiment and theory through the resolution of the radiative transfer equation, is based on the comparison between the experimental and the simulated profiles of the 308.21 and 396.15 nm Al(I) resonant lines. Special attention has been turned to the ion and electron Stark broadening and self-absorption effects. An important departure from equilibrium is put into evidence throughout the plasma recombination. The measurement of the aluminum fundamental state which is of prime importance in the validation of any collisional-radiative model dedicated to this complex situation has been carried out in a large pressure range (5 to 10⁵ Pa). The measurement of the relaxation times highlights the major role played by the diffusion in the relaxation of the plasma species. (author)