  Experimental characterization and comparison of the temporal features of
plasma produced by ultrafast (100 fs, 800 nm) and short-pulse (7ns, 1064 nm)
laser pulses from a high purity nickel and zinc targets, expanding into a
nitrogen background, are presented. The experiment is carried out under a wide
pressure range of 10^-6 to 10^2 Torr, where the plume intensity is found to
increase rapidly when the pressure approaches 1 Torr. Electron temperature (Te)
is calculated from OES and is found to be independent of pressure for ultrafast
excitation, whereas an enhancement in Te is observed around milliTorr regime
for short-pulse excitation.The velocity measurements indicate acceleration of
the fast species to a certain distance upon plume expansion, whereas the slow
species are found to decelerate, particularly at higher pressures.A comparison
of the time of flight dynamics of neutrals and ions in the LPPs generated by
intense laser pulses confirms that the fast species observed are due to the
recombination of fast ions with relatively slow moving electrons. Furthermore,
an asynchronous pump-probe scheme is employed in the experiment that uses a
Q-switched (1064 nm, 7ns) laser for plasma generation and the plasma thus
generated is probed using a low power 100 fs, 82 MHz pulse train, which allows
the probing of the transient LPP at every 12 ns intervals.
