EMISSION CHARACTERISTICS AND DYNAMICS OF C-2 FROM LASER-PRODUCED GRAPHITE PLASMA

The emission features of laser ablated graphite plume generated in a h elium ambient atmosphere have been investigated with time and space re solved plasma diagnostic technique. Time resolved optical emission spe ctroscopy is employed to reveal the velocity distribution of different species ejected during ablation. At lower values of laser fluences on ly a slowly propagating component of C-2 is seen. At high fluences emi ssion from C-2 shows a twin peak distribution in time. The formation o f an emission peak with diminished time delay giving an energetic peak at higher laser fluences is attributed to many body recombination. It is also observed that these double peaks get modified into triple pea k time of flight distribution at distances greater than 16 mm from the target. The occurrence of multiple peaks in the C-2 emission is mainl y due to the delays caused from the different formation mechanism of C -2 species. The velocity distribution of the faster peak exhibits an o scillating character with distance from the target surface. (C) 1997 A merican Institute of Physics.