CoRaM-Al: a Collisional-Radiative model dedicated to aluminum laser-induced plasma

A nonlinear time-dependent Collisional-Radiative (CR) model is elaborated in the purpose of understanding the behavior of the plasma created during a Laser Induced Breakdown Spectroscopy (LIBS) experiment when a nanosecond pulse (4 ns at 532 nm and 65 mJ) is focused on an aluminum sample with uence approximatively equal to 2 10 W m . The underlying interaction is modeled from the moment of the beginning of the sample vaporization until the nal recombination phase. The plasma is assumed in thermal and chemical non equilibrium: (1) electrons and heavy particles (aluminum ions to the Al ion and atoms) are in Maxwell-Boltzmann equilibrium with di erent temperatures and (2) the heavy particles are neither in Boltzmann nor in Saha equilibrium with electrons. The electronic excited states are considered independent and behave freely. The whole is coupled by collisional and radiative elementary processes: by this way, it is possible to follow in time the dynamic of the plasma and to observe the possible departure from equilibrium. We show that the plasma equilibrium is obtained with di culty even if the electron density is high owing to the persistence of the initial strong non equilibrium.