Temporal Characterization of a Plasma Produced by Interaction of Laser Pulses with Water Solutions

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 T_e using a Saha-Boltzmann analysis. The broadening of the resonance line of CaI at 4227 Å was used to deduce the electronic density N_e, with the aid of the semiclassical theory of Stark broadening. A value of T_e ≈ 28000 K decreasing slightly to 21000 K, and an exponential decay for N_e were found, with N_e ≈ 1:25 × 10¹⁸ cm^-3 at 500 ns and τ_e = (1200 ± 50) ns.