A new approach of quantitative analysis of liquid sample using laser ablation technique was developed. The liquid was immediately freezed using the mixture of dry ice and alcohol in weight ratio of 95% : 5%. As a result, an increase of the repulsion force from the sample surface will enable the generation of the laser-induced shock wave plasma which was difficult to carry out on liquid surface. The ice sample was then irradiated using Nd-YAG laser operated in its fundamental wavelength. In order to increase the signal to background ratio and to obtain a sharp atomic line spectra, helium gas was used instead of air. Dynamic characterization of the spatially integrated time profile of the Cu I 521.8 nm, Cu I 510.5 nm and H α lines shows a shock excitation stage and cooling stage which is corresponded to our shock wave model even when the plasma was generated under atmospheric gas pressure. Further study of the time profile averaged temperature of the atmospheric plasma also shows an increase of temperature during the shock excitation stage followed by diminution of temperature during the cooling stage. An application of this technique was then applied to quantitative analysis of several liquid samples. A linear calibration curve which intercept at 0 point was obtained for all of the elements investigated in this study such as sodium, potassium, lithium, copper, silver, lead and aluminum. A detection limit of around 1 ppm was found for the above element. This new technique will contribute to a great extent of laser atomic emission spectrochemical analysis for liquid samples.

An experimental study has been carried out on the dynamical process taking place in the plasma generated by a Qswitched Nd-YAG laser (1,064 nm, 8 ns, 175 mJ) on a water surface at atmospheric air pressure. Accurate dynamical characterization of the resulting plasma has been carried out using gated intensified optical multichannel analyzer. The occurrence of the hydrogen emission lines of H I 656.2 nm (Ha), H I 486.1 nm (Ho), H I 434.0 nm (Hr) and H I 410.1 nm (H5) was observed. Line broadening of hydrogen emission lines was studied in term of its emission time profile. In addition to reaffirming the role of the shock wave mechanism in the generation of atmospheric plasma, an analysis of the time-resolved spatial integrated of emission intensities and the time-resolved averaged temperature was made using the emission lines of Cu I 5 10.5 nm and Cu I 521.8 nm. As a result, the occurrence of two-stage emission processes, the shock excitation stage and cooling stage has been proved. The experimental result considering the characteristics of the atmospheric plasma can be well understood by considering the shock wave model instead of breakdown mechanism. Further application for quantitative analysis of calcium and sodium in water was also performed. A linear calibration curve was obtained without using any internal standardization and the detection limit in this stage of the experiment was estimated to be less than 1 ppm for calcium and sodium in water.