Investigation of the mechanisms involved in formation and decay of laser-produced plasmas

An analysis has been carried out on single and double pulse laser-induced plasma spectroscopy (LIPS) of aluminium samples in air. Spectroscopic techniques were used to retrieve relevant plasma characteristics during the first few microseconds after the plasma ignition. With respect to single laser excitation, dramatic changes in plasma characteristics were observed in the double pulse regime at 1.2 GW cm−2. Above this threshold, the narrowing of both atomic and ionic lines, the increase of the line emission intensity with longer time decays and a higher plasma stability were observed. The different threshold behaviour following single and double pulse excitation is discussed in terms of the optical and physical properties of the laser plasma produced.