Shock wave plasma induced by TEA CO2 laser bombardment on glass samples athigh pressures

An experimental study has been carried out on the dynamical process taking place in laser plasma, generated by TEA CO2 laser (400 mJ, 100 ns) irradiat ion on glass samples surrounding by air of high pressures up to 760 torr. A ccurate dynamical characterization was performed by simultaneous observatio n of the plasma emission front and the shock wave front. The shock wave fro nt was detected by a modified shadowgraph technique while the emission fron t was detected by observing the rising time at various slit positions. In s pite of the occurrence of a new feature uncommon to laser plasma, generated in low air pressures, it is found that the two fronts coincide and move to gether at the initial stage of the laser plasma, but eventually separate fr om each other, with the emission front being left behind the shock wave fro nt at a later stage. These characteristics hold for the atomic emission lin es of all elements contained in the glass samples examined, regardless of t heir different atomic weights. It is therefore strongly indicative of the s hock wave mechanism in the laser plasma generation and the emission in the high-pressure surrounding air. (C) 2000 Elsevier Science B.V. All rights re served.