A TIME-RESOLVED SPECTROSCOPIC STUDY ON THE SHOCK-WAVE PLASMA-INDUCED BY THE BOMBARDMENT OF A TEA CO2-LASER

A TEA CO2 laser (500 mJ, 100 ns) has been focused on Zn plate in a surrounding gas at 0.5 Torr. The characteristics of the laser plasma were analysed using a unique time-resolved spectroscopic method. Time-resolved spatial distributions of Zn I 481.0 nm and Zn II 492.4 nm emission lines were observed. It was clearly shown that the resulting plasma has a thin shell structure and expands with time, and the ionization of Zn atoms preceeds at slower rate than the excitation of neutral Zn atoms. The displacement of the neutral Zn emission was proportional to the two-fifths power of time. These experimental results proved that the plasma was excited by a blast wave induced by the laser bombardment.