Temporal and spatial evolution of Ca in laser induced plasma from graphite target

Laser ablation of graphite has been carried out using 1.06 mu m radiation from a Q-switched Nd:YAG laser and the time of flight distribution of molecular C-2 present in the resultant plasma is investigated in terms of distance from the target as well as laser fluences employing time resolved spectroscopic technique. At low laser fluences the intensities of the emission lines from C-2 exhibit only single peak structure while beyond a threshold laser fluence, emission from C-2 shows a twin peak distribution in time. The occurrence of the faster velocity component at higher laser fluences is explained as due to species generated from recombination processes while the delayed peak is attributed to dissociation of higher carbon clusters resulting in the generation of C-2 molecule. Analysis of measured data provides a fairly complete picture of the evolution and dynamics of C-2 species in the laser induced plasma from graphite. (C) 1996 American Institute of Physics.