Emission distributions of laser-ablated particle pulses from a binary system and its single components

The present experiment for the first time compares in detail emission characteristics of laser-produced plasma pulses ablated from a binary material with those of its pure components. As an example system we have chosen a tungsten-copper alloy (W34Cu66). The plasma was produced by obliquely incident Q-switched pulses (EL=170 mJ, τ=5 ns and λ=1.06 μm) focused to an ablation area of 1.74 mm2. The most remarkable results are: the angular emission distribution of the totally ablated mass of the binary system W34Cu66 is almost equal to that of pure copper, i.e. the lighter component of the composite, and no segregation effect is observed between W and Cu. These findings are in contrast to published experimental results and simulation models so far. Additional findings are that the angular distributions of the average kinetic energies are similar for corresponding ions Wq+ and Cuq+ ablated from either the compound system or the single component targets Cu and W, respectively and that stoichiometry appears to be conserved in the composite at least for the ions during ablation and expansion. (author)