Spatial distributions of electron density in microplasmas produced by laser ablation of solids

The spatial distribution of electron density in argon microplasmas produced by laser ablation of solids has been investigated by time-resolved emission spectroscopy. The electron density was derived from Stark broadening and shift of spectral lines. It was found that the radial gradient of the electron density is much smaller than the gradient of the atomic number density of atoms ablated by the laser into the plasma. The almost homogeneous plasma conditions in the centre of the microplasmas are essential for quantitative element analysis of solid samples by laser ablation. On the other hand, because of the homogeneous conditions microplasmas are excellent sources for measurements of reliable Stark broadening and shift parameters of atomic and ionic spectral lines of all elements which can be ablated by lasers from solid samples.