Harilal, S S; Issac, Riju C; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(Pramana, September , 1997)
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Abstract:
Time resolved optical emission spectroscopy is employed to study the expansion
dynamics of C2 species in a graphite plasma produced during the Nd : YAG ablation. At low laser
fluences a single peak distribution with low kinetic energy is observed. At higher fluences a twin
peak distribution is found. It has been noted that these double peak time of flight distribution splits
into a triple peak structure at distances >_ 17mm from the target surface. The reason for the
occurrence of multiple peak is due to different formation mechanisms of C2 species
Harilal, S S; Issac, Riju C; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(IOP, 1997)
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Abstract:
Time and space resolved spectroscopic studies of the molecular band
emission from C2 are performed in the plasma produced by irradiating a graphite
target with 1:06 m radiation from a Q-switched Nd:YAG laser. High-resolution
spectra are recorded from points located at distances up to 15 mm from the target
in the presence of ambient helium gas pressure. Depending on the laser
irradiance, time of observation and position of the sampled volume of the plasma
the features of the emission spectrum are found to change drastically. The
vibrational temperature and population distribution in the different vibrational levels
of C2 molecules have been evaluated as a function of distance for different time
delays and laser irradiance. It is also found that the vibrational temperature of C2
molecules decreases with increasing helium pressure.
Harilal, S S; Issac, Riju C; Bindhu, C V; Nampoori, V P N; Vallabhan, C P G(American Institute of Physics, September 15, 1996)
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Abstract:
Laser ablation of graphite has been carried out using 1.06mm radiation from a Q-switched Nd:YAG
laser and the time of flight distribution of molecular C2 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 C2 exhibit
only single peak structure while beyond a threshold laser fluence, emission from C2 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 C2 molecule.
Analysis of measured data provides a fairly complete picture of the evolution and dynamics of
C2 species in the laser induced plasma from graphite.