Experimental and theoretical investigation of a self-absorbed spectral line emitted from laser-induced plasmas

Using well-known expressions describing radiative transfer, we have established an expression predicting the spectral profile of a self-absorbed Ca++ 393.4 nm emission line as emitted by a transient laser-induced plasma. In this approach, the plasma was approximated as comprising five distinct layers, each of thickness 0.5 mm, and each characterized by a unique uniform electron density, electron temperature, and optical depth. The validity of the theoretical model was confirmed by successful comparison with experimental data. Inhomogeneous laser-induced plasmas were produced on the surface of an aqueous CaCl2 (0.01 mol/l) solution using a frequency-doubled Nd:YAG laser. Optical emission spectra were collected in such a way as to allow for temporal and spatial diagnostics of the plasma plumes. (C) 2010 Optical Society of America