Dynamics of laser-produced carbon plasma in an inert atmosphere

Time- and space-resolved emission spectroscopy measurements were performed to investigate plasma dynamics during laser evaporation of a graphite target. The evolution of the velocity and the emission intensity of the excited species versus the distance and the pressure of the foreign gas are studied. The time-resolved emission intensity of C II* transition at 426.7 nm shows a double-peak structure, resulting from the stratification of the plasma into fast and slow components. Intense molecular emission is found to occur behind a front separating the plasma from the foreign gas. Two stages of expansion are found in the generated plume, the first one starting just after the laser irradiation, the second beginning some time later depending on the nature and the pressure of the foreign gas. The two stages are well described, using a viscous drag force model for the first one and a delayed ideal blast wave model for the second. (C) 1996 American Institute of Physics.