CORRELATION OF SPECTRAL EMISSION INTENSITY IN THE INDUCTIVELY-COUPLED PLASMA AND LASER-INDUCED PLASMA DURING LASER-ABLATION OF SOLID SAMPLES

Spectral atomic emission intensity from laser-induced plasmas (LIPs) exhibits excellent correlation with atomic emission intensity in the inductively coupled plasma (ICP) for a wide variety of materials and laser powers. Laser ablation sampling with introduction into an ICP for chemical analysis has, among other factors, a strong nonlinear dependence on laser energy, spot size, and material composition. The LIP emission also has a similar nonlinear dependence and is shown to correspond with the ICP behavior. The correlation is demonstrated for several homogeneous metallic and oxide materials during laser ablation sampling over a range of power densities and incident laser beam spot sizes. The correlation is best for higher melting temperature materials and moderate laser power density. The LIP and ICP emission intensities both show similar dependence for mass ablation rate versus power density and laser beam spot size. A normalized ICP/area over LIP emission ratio shows that a functional relationship can be found for changes in ICP intensity with changes in laser power density. The correlation shows that the ICP intensity accurately reflects changes in the laser ablation process and that the LIP may possibly be used for internal monitoring during laser sampling with the ICP.