Diagnostics of KrF- and Nd:YAG-Laser Produced Carbon Plumes by Time- and Spatially-Resolved Spectroscopy

Graphite was ablated by three lasers and the resultant carbon plumes were investigated by time- and spatially-resolved spectroscopy. A KrF excimer laser (248 nm) and an Nd:YAG laser (1064 and 266 nm) were used. Near the target surface, C2 (Swan band) and ionic emissions from the plume produced by the 1064-nm laser at a fluence of 6 J/cm2 were stronger than those produced by the 248-nm and 266-nm lasers. The C emission lines (247.9 and 193.1 nm) produced by the KrF excimer laser were stronger than those produced by the other lasers. The most probable velocity of C+ was highly dependent upon the laser wavelength. The dependence of the most probable velocity on the fluence was small. The velocity of C+ ablated by the 248-nm laser was twice as fast as that ablated by the 1064-nm laser, when the fluence of the 1064-nm laser was six times as large as that of the 248-nm laser.