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EXCITATION MECHANISM IN THE GENERATION OF LASER INDUCED ATMOSPHERIC PLASMA IN WATER SAMPLE

M.I.Y. Ichwan1, T.J. Lie2, H. Suyanto3, R. Hedwig4, M. Pardede5, M.O. Tjia6, K. Kagawa7 and H. Kurniawan8

1Department of Physics, 10 November Institute of Technology, Jl. Arief Rahman Hakim, Keputih, Surabaya 60111, Indonesia
2Meridien Counseling, Jl. Taman Sari Raya 85P, Jakarta 11150, Indonesia
3Department of Physics, Udayana University, Bukit Jimbaran, Bali, Indonesia
4Hardware Laboratory, Department of Computer Engineering, Bina Nusantara University, 9 KH. Syahdan, Jakarta Barat 11480, Indonesia
5Department of Electronic Engineering, University of Pelita Harapan, UPH Tower Lippo Karawaci, Tangerang, Indonesia
6Department of Physics, Bandung Institute of Technology, Jl. Ganesha 10, Bandung, Indonesia
7Department of Physics, Faculty of Education and Regional Studies, Fukui University, 9-1 bunkyo 3-chome, Fukui 910, Japan
8Research Center of CV. Maju Makmur Mandiri, 40 Srengseng Raya, Kembangan, Jakarta Barat 11630, Indonesia

Abstract
An experimental study has been carried out on the dynamical process taking place in the plasma generated by a Q-switched 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 (Halpha), H I 486.1 nm (Hbeta), H I 434.0 nm (Hgamma) and H I 410.1 nm (Hdelta) was observed. Line broadening of the 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 510.5 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. Additional application of this technique was also applied by freezing the water sample immediately by means of a mixture of dry ice and alcohol of purity of 99%. Linear calibration curve was also obtained for several heavy metals with extremely low detection limit.

Publication : Physics Journal IPS A7 (2004) 0403
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Additional info : 9 pages, language English