Insights in the laser-induced breakdown spectroscopy signal generation underwater using dual pulse excitation - Part I: Vapor bubble, shockwaves and plasma

► Primary plasma during the first μs is irregular due to particle expulsion. ► Later the plasma grows into the evolving bubble, its emission lasts more than 30 μs. ► The initial shockwave and its echoes alter locally the refraction index. ► Defocusing by the bubble apparently reduces the dimensions of the secondary plasma. ► Reflections at the bubble wall redistribute the intensity of the secondary plasma.