Distributions of C2 and C3 radical densities in laser-ablation carbon plumes measured by laser-induced fluorescence imaging spectroscopy

We measured temporal variations of the distributions of C-2 and C-3 radical densities in carbon plumes produced by laser ablation of graphite in ambient He gas. Laser-induced fluorescence imaging spectroscopy was used for the measurement. The temporal variations of total numbers of C-2 and C-3 contained in plumes were evaluated by integrating the density distributions. The experimental observations have shown that the gas-phase production of C-2 is comparable to the direct production from the target, while C-3 is mainly produced in gas phase by three-body reactions between C and C-2. In addition, we have discussed a scenario for the temporal evolution of heavy clusters (C-n with ngreater than or equal to4). The present results are useful for understanding initial formation processes of carbon clusters in laser-ablation plumes. (C) 2002 American Institute of Physics.