PREFERENTIAL VAPORIZATION DURING LASER-ABLATION INDUCTIVELY-COUPLED PLASMA-ATOMIC EMISSION-SPECTROSCOPY

The Zn-to-Cu ratio in brass was measured by laser ablation inductively coupled plasma atomic emission spectroscopy. The influence of laser b eam properties (pulse width, wavelength, and power density) on fractio nal laser ablation was investigated. The behavior of the Zn/Cu ratio v s, laser power density shows that there are different mechanisms influ encing ps and us laser ablation. With the use of a 30 ns pulse duratio n from an excimer laser, thermal vaporization appears to be the domina nt process in the low-power density region. The Zn/Cu ratio approaches stoichiometry at higher power density, but the ablated mass still rem ains Zn rich. With a 35 ps pulse Nd:YAG laser, a nonthermal mechanism appears to govern the laser ablation process. When a 3 ns Nd:YAG laser is used, both thermal and nonthermal processes exist. For both 3 us a nd 30 ps Nd:YAG lasers, stoichiometric ablation can be achieved at hig her power densities.