Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

Stefan Trautner; Juraj Jasik; Christian G Parigger; Johannes D Pedarnig; Wolfgang Spendelhofer; Johannes Lackner; Pavel Veis; Johannes Heitz

doi:10.1016/j.saa.2016.11.045

Laser-induced optical breakdown spectroscopy of polymer materials based on evaluation of molecular emission bands

Spectrochim Acta A Mol Biomol Spectrosc. 2017 Mar 5:174:331-338. doi: 10.1016/j.saa.2016.11.045. Epub 2016 Dec 2.

Authors

Stefan Trautner¹, Juraj Jasik², Christian G Parigger³, Johannes D Pedarnig¹, Wolfgang Spendelhofer⁴, Johannes Lackner⁴, Pavel Veis⁵, Johannes Heitz⁶

Affiliations

¹ Institute of Applied Physics, Johannes Kepler University, Altenberger Straße 69, 4040 Linz, Austria.
² Institute of Applied Physics, Johannes Kepler University, Altenberger Straße 69, 4040 Linz, Austria; Department of Organic Chemistry, Charles University in Prague, Hlavova 2030/8, 128 43 Prague 2, Czech Republic; Center for Laser Applications, The University of Tennessee Space Institute, Tullahoma, TN 37388-9700, USA.
³ Center for Laser Applications, The University of Tennessee Space Institute, Tullahoma, TN 37388-9700, USA.
⁴ KRAIBURG Austria GmbH & Co. KG, 5132 Geretsberg, Austria.
⁵ Department of Experimental Physics, Physics and Informatics, Comenius University, Mlynska dolina F2, 842 48 Bratislava, Slovakia.
⁶ Institute of Applied Physics, Johannes Kepler University, Altenberger Straße 69, 4040 Linz, Austria. Electronic address: johannes.heitz@jku.at.

PMID: 27984754
DOI: 10.1016/j.saa.2016.11.045

Abstract

Laser-induced breakdown spectroscopy (LIBS) for composition analysis of polymer materials results in optical spectra containing atomic and ionic emission lines as well as molecular emission bands. In the present work, the molecular bands are analyzed to obtain spectroscopic information about the plasma state in an effort to quantify the content of different elements in the polymers. Polyethylene (PE) and a rubber material from tire production are investigated employing 157nmF₂ laser and 532nm Nd:YAG laser ablation in nitrogen and argon gas background or in air. The optical detection reaches from ultraviolet (UV) over the visible (VIS) to the near infrared (NIR) spectral range. In the UV/VIS range, intense molecular emissions, C₂ Swan and CN violet bands, are measured with an Echelle spectrometer equipped with an intensified CCD camera. The measured molecular emission spectra can be fitted by vibrational-rotational transitions by open access programs and data sets with good agreement between measured and fitted spectra. The fits allow determining vibrational-rotational temperatures. A comparison to electronic temperatures T_e derived earlier from atomic carbon vacuum-UV (VUV) emission lines show differences, which can be related to different locations of the atomic and molecular species in the expanding plasma plume. In the NIR spectral region, we also observe the CN red bands with a conventional CDD Czerny Turner spectrometer. The emission of the three strong atomic sulfur lines between 920 and 925nm is overlapped by these bands. Fitting of the CN red bands allows a separation of both spectral contributions. This makes a quantitative evaluation of sulfur contents in the start material in the order of 1wt% feasible.

Keywords: LIBS; Laser-induced breakdown spectroscopy; Molecular emission spectroscopy; Polyethylene; Rotational-vibrational analysis; Rubber from tire production.