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K: Fachverband Kurzzeitphysik
K 2: Gasdynamik / Laser-Materie-Wechselwirkung
K 2.3: Talk
Monday, March 30, 2009, 15:30–15:45, HS Physik
F2-Laser LIBS Analysis of Polymer Materials — •Johannes Heitz1, Juraj Jasik1,2, Johannes D. Pedarnig1, and Pavel Veis2 — 1CD-Laboratory Laser-Assisted Diagnostics, Institute of Applied Physics, Johannes Kepler University Linz, Austria — 2Faculty of Mathematics, Physics and Informatics, Comenius University, Bratislava, Slovakia
Laser-induced breakdown spectroscopy (LIBS) is employed for the detection of trace elements in polyethylene (PE). For effective laser ablation of PE, we use a F2 laser (wavelength 157 nm) with a laser pulse length of 20 ns, a pulse energy up to 50 mJ, and pulse repetition rate of 10 Hz. The optical radiation of the laser induced plasma is measured by a VUV spectrometer with a detection range down to a wavelength of 115 nm. A gated photon-counting system is used to acquire time resolved spectra. The VUV LIBS spectra of PE are dominated by strong emission lines of neutral and ionized Carbon atoms. From time-resolved measurements of the Carbon line intensities, we determine the temporal evolution of the electronic plasma temperature, Te. For this, we use Saha-Boltzmann plots with the electron density in the plasma, Ne, derived from the broadening of the Hydrogen H-alpha line. With the parameters Te and Ne, we calculate the intensity ratio of the atomic Sulphur and Carbon lines at 180.7 nm and at 175.2 nm, respectively. The calculated intensity ratios are in good agreement with the experimentally measured results.
The co-operation is performed in the frame of the "Scientific and Technological Agreement WTZ Austria - Slovakia".