Spatial and temporal evolution of laser-generated microplasmas

A study of the evolution of microplasmas produced on aluminum alloy surface at ambient air pressure by 266-nm 10-ns laser pulses with energies of 3 to 100 [micro]J (2 to 68 GW/[cm.sup.2]) is carried out. Gated photography with a minimum width of 5 ns is used to investigate the plasma evolution. Plasma emission and plasma distances from the sample surface are investigated as a function of time. Pulse energy has a strong effect on plasma emission particularly at short delay times. The experimental results are compared with a simplified model of plume expansion. Index Terms--Ablation, imaging, laser-induced breakdown spectroscopy (LIBS), plasma expansion.