UV-laser plasma study of elemental distributions of paper coatings

The potential of a laser-generated plasma method in the analysis of coating coverage, coatweight distribution, and 3D distribution of various pigments of paper coating is described. A XeCl-excimer laser (308 nm) was used to generate microscopic plasma from the paper coating, and delayed detection of silicon and calcium atomic emission line intensities was used as a measure of mass vaporized. Macroscopic areas typically 10 x 10 mm(2) at a spatial resolution of 250 mu m were studied. With a single laser pulse (0.2 mJ of energy), about 2 ng of coating from a volume of 30 mu m in diameter and 2 mu m in depth was vaporized. The method seems to be useful for characterization of multilayer coatings.