Sony, George; Ajai, Kumar; Singh, R K; Nampoori, V P N(Springer, 2010)
[+]
[-]
Abstract:
A study has been carried out to understand the
influence of ambient gases on the dynamics of laser-blow-off
plumes of multi-layered LiF–C thin film. Plume images
at various time intervals ranging from 100 to 3000 ns have
been recorded using an intensified CCD camera. Enhancement
in the plume intensity and change in size and shape
occurs on introducing ambient gases and these changes are
highly dependent on the nature and composition of the ambient
gas used. Velocity of the plume was found to be
higher in helium ambient whereas intensity enhancement is
greater in argon environment. The plume shapes have maximum
size at 10−2 and 10−1 Torr of Ar and He pressures,
respectively. As the background pressure increases further
(>10−2 Torr: depending on the nature of gas), the plume
gets compressed/focused in the lateral direction. Internal
structure formation and turbulences are observed at higher
pressures (>10−1 Torr) in both ambient gases.
Harilal, S S; Issac, Riju C; Bindhu, C V; Pramod, Gopinath; Nampoori, V P N; Vallabhan, C P G(Elsevier, 1997)
[+]
[-]
Abstract:
Time and space resolved studies of emission from CN molecules have been carried out in the plasma produced from
graphite target by 1.06 urn pulses from a Q-switched Nd:YAG laser. Depending on the laser pulse energy, 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 have
been studied as functions of distance, time, laser energy and ambient gas pressure. Evidence for nonlinear effects of
the plasma medium such as self focusing which exhibits threshold-like behaviour are also obtained. Temperature and
electron density of the plasma have been evaluated using the relative line intensities of successive ionization stages of
carbon atom. These electron density measurements are verified by using Stark broadening method.