Sub-target effect in film analysis using TEA CO2 laser-induced plasma

Hydrogen analysis in solid samples by utilizing He metastable atoms induced by TEA CO2 laser plasma in He gas at 1 atm

“…In this experiment, a brass plate was placed on the backside of the sample in a close contact as a sub-target to enhance the ablation speed. In our previous works, for TEA CO 2 laser bombardment, it was proved that for soft samples, the use of a metal sub-target was essential to overcome the low ablation speed due to the lack of repulsive force [18,[31][32][33]. In fact, in this experiment, fluorine emission cannot be detected when the sub-target was not used even though a crater actually formed on the sample surface.…”

“…As compared to an Nd-YAG laser case, unique phenomena take place in plasma generation using the TEA CO 2 laser due to the long wavelength (means low frequency) of 10.6 μm and its rather long pulse duration of around 200 ns. This specific characteristics in some cases are effectively used as the source for laser-induced plasma spectrometry which otherwise never happens in an Nd-YAG laser case [18]. In this work, the TEA CO 2 laser was employed to generate much stronger, enlarged volume He gas breakdown plasma in which the helium excited metastable state is expected to produce overwhelmingly.…”

New Technique for the Direct Analysis of Food Powders Confined in a Small Hole Using Transversely Excited Atmospheric CO2 Laser-Induced Gas Plasma

“…On the other hand, a broad band responsible for the emission line of a C-H cluster also appears. 15 Along with the host emission lines contained in the milk powder, the spectrum also displays the ionic emission line of nitrogen coming from the surrounding gas. This is supported by another experiment in which helium was used in place of the nitrogen surrounding gas; namely, no emission from this line was observed when the experiment was carried out under helium as the surrounding gas.…”

Analysis of Heavy Metal Pollution in Soil Using Transversely Excited Atmospheric CO2 Laser-Induced Plasma by Trapping the Soil in Microstructured Holes on Metal Subtargets

“…One may think to utilize the subtarget effect from a metal plate to make a sufficient dissociation by spreading the small soil particles on the metal plate in the same manner as we employed in the film analysis described above. 11,12 However, it was confirmed in this experiment by carrying out the analysis on the small soil particles with moisture at some level painted directly on a nickel subtarget, that though a strong plasma can be generated due to the metalinduced gas breakdown plasma, the detection sensitivity of the pollutant emission was not much improved. This fact implies that the atomizing process of the impurity existing inside the small soil particles could not take place effectively, as illustrated in Fig.…”

“…10 The subtarget effect is a unique phenomenon taking place in the case of using a TEA CO 2 laser, as reported elsewhere. 11,12 When the TEA CO 2 laser was focused directly on a soft sample, almost no appreciable plasma formation took place. However, when the soft material was attached to the surface of a hard subtarget, such as a metal plate, in the form of a thinner layer, a strong plasma was produced, leaving the metal plate without any ablation or damage.…”