The time- and space-resolved emission profiles of LiI and LiII emission lines from the laser-blow-off plumes of a multilayered LiF–C thin film have been studied using spectroscopic technique. The evolution features were analyzed in different ambient environments ranging from high vacuum to 3mbars of argon pressures and at various fluences of the ablating laser. During the evolution of the plume, a transition region was found to exist between 4 and 6mm. Here, the plume dynamics changed from free expansion to collisional regime, where the plume experienced viscous force of the medium. The enhancement observed in neutral lines, in comparison with ionic lines, is explained in terms of the yield difference in electron impact excitation and ionization processes. Substantial difference in the arrival time distribution of the plume species was observed for LiI and LiII lines at high ambient pressures. Three expansion models are invoked to explain the evolution of the plume in different ambient conditions. The laser fluence was found to control the ratio of ions and neutrals.

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The time and space resolved emission profiles of the CII line from the laser-blow-off (LBO) plumes of multilayered LiF-C thin film have been investigated using a laser-induced forward transfer technique. The evolution features of the 426.7 nm line were studied in different ambient environments ranging from high vacuum to 3 mbar of argon pressures and at various fluences of the ablating laser. It was found that many features of the plasma plume generated by the LBO method resemble that of plumes created in conventional laser produced plasma; however, a few differences were observed in their behaviour with regard to plume splitting and plume compression. A sudden change in the temporal profile was observed to occur at a distance about 4–6 mm away from the target. The variation of the plume structures observed at different fluences of the ablating laser is reported. The validity of the Rayleigh–Taylor instability, shock wave and drag force model in the present experiment are also discussed.

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