We have proposed scheme to detect trace elements analysis in pure water, in which the excimer laser ablation technique is combined with the laser induced atomic fluorescence spectroscopy. Theoretical estimation predicts very high sensitivity of this method, because the excimer laser ablation can generate high density atoms in the low background radiation. Sensitive detection of Na atoms is demonstrated by using this method in low pressure helium, and detection limit of 1.7 ppt is obtained. The same experiment is made under the open air condition, by using the ablation in a He supersonic jet and the detection limit less than 1ppb is attained.
The effect of laser focusing on the emission characteristics of a Nd: YAG laser-produced plasma in argon at reduced pressure was studied by changing the distance between the laser focal point and the sample surface. The result obtained showed that maximum emission intensity was obtained at tight focusing of the laser radiation at 100 Torr, and that laser defocusing brought about no improvement in the analytical signal.