The temporal evolution of a plasma formed by the interaction of a Nd-YAG 10 ns laser pulse with the surface of aqueous solutions of CaCl2, has been observed by analyzing the variation of the emission spectra of ions and neutral atoms in the time interval after the laser pulse, 500 ns < t < 5000 ns. The intensity measurements of the lines of CaII at 3158 Å, 3179 Å, 3706 Å, 3736 Å, 3933 Å, 3968 Å were used to obtain the electronic temperature Te using a Saha-Boltzmann analysis. The broadening of the resonance line of CaI at 4227 Å was used to deduce the electronic density Ne, with the aid of the semiclassical theory of Stark broadening. A value of Te ≈ 28000 K decreasing slightly to 21000 K, and an exponential decay for Ne were found, with Ne ≈ 1:25 × 1018 cm-3 at 500 ns and τe=(1200±50) ns.

Emission spectra of MgI and MgII from a plasma induced by the interaction of a laser pulse with the surface of aqueous solutions of MgCl 2 , were recorded by a time resolved spectroscopy method to obtain information on the processes involved in the formation and the evolution of the two different species. A kinetic model based on ion-electron recombination produced during the relaxation of the plasma is constructed with the aim to explain the origin and the temporal shift of observed Mg þ and Mg emissions. Comparison with the experimental results is presented and discussed.

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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 CaCl(2) (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.

In this paper, we propose and use an experimental method permitting the measurement of optical depth of a selfabsorbed spectral line emitted from laser-induced plasma on the surface of an aqueous solution. Using well-known equations describing the radiatif transfer and the evolution with the optical depth of the relative uncertainty on the measurement of line intensity and on the half width at half maximum, we have also deduced the uncertainty on the measurement of electron temperature and the electron density. An application to the diagnostics of this plasma has been realized, and we show the reliability of the spectroscopic measurements.