PREFERENTIAL VAPORIZATION AND PLASMA SHIELDING DURING NANO-SECOND LASER-ABLATION

Preferential removal of components from mixed material targets and pla sma shielding are studied by using inductively coupled plasma-atomic e mission spectrometry (LCP-AES) during UV nano-second laser ablation. T he ICP emission intensity for Cu and Zn during ablation of brass sampl es varies versus laser power density. A model using thermal evaporatio n and inverse Bremsstrahlung processes is presented. The model shows t hat plasma shielding occurs at approximately 0.3 GW/cm(2), in agreemen t with experimental data for change in the mass ablation rate. The goo d agreement of model and experimental data suggest that thermal effect s are important during nano-second laser ablation for power density le ss than 0.3 GW/cm(2).