Spectrochimica Acta Part B 57 (2002) 137–146 0584-8547/02/$ - see front matter  2002 Elsevier Science B.V. All rights reserved. PII: S0584-8547 ( 01 ) 00359-7 Diode laser-aided diagnostics of a low-pressure dielectric barrier discharge applied in element-selective detection of molecular species K. Kunze , M. Miclea , G. Musa , J. Franzke , C. Vadla , K. Niemax * a a b a c a, Institute of Spectrochemistry and Applied Spectroscopy (ISAS), Bunsen-Kirchoff-Strasse 11, 44139 Dortmund, Germany a National Institute for Laser, Plasma and Radiation Physics, 76900 Bucharest-Marguele, Romania b Institute of Physics, Bijenicka 46, HR-10000, Zagreb, Croatia c Received 16 July 2001; accepted 18 September 2001 Abstract A small, low-pressure dielectric barrier discharge used as a detector for the analysis of halogenated hydrocarbons was studied by diode laser absorption spectroscopy of excited plasma atoms. The distribution, as well as diffusion of the excited atoms, was measured with high spatial and temporal resolution. The major part of the excited atoms was found in a very narrow discharge volume, where the maximum gas temperature and electron density, determined from broadening of the absorption line profiles, were approximately 1000 K and greater than 10 cm , respectively. 15 y3  2002 Elsevier Science B.V. All rights reserved. Keywords: Dielectric barrier discharge; Diode laser absorption spectrometry; Plasma diagnostics; Halogenated hydrocarbons 1. Introduction We recently reported on the application of a small, low-pressure dielectric barrier discharge (DBD) for the analysis of CCl F , CClF and 2 2 3 CHClF by diode-laser atomic absorption spec- 2 trometry (DLAAS) of chlorine and fluorine w1x. It was demonstrated that the analytical figures of merit of DLAAS in a DBD are comparable with data obtained using microwave-induced plasmas (MIP), although the DBD was operated at much lower power (-1W) than for MIPs. It was particularly surprising that the DBD was found to * Corresponding author. Fax: q49-231-1392-310. E-mail address: niemax@isas-dortmund.de (K. Niemax). be very efficient for dissociation of the halogenated hydrocarbons. The present paper is devoted to plasma diagnos- tics of the low-pressure DBD. This is a challenging task, since the electrode distance of the discharge is very small (1 mm) and the processes in the AC plasma are highly transient. Although DBDs close to atmospheric pressure are widely used, for exam- ple, in flat-panel plasma displays for color TV screens w2x or for industrial production of ozone w3x, the plasma processes are yet not fully under- stood. There are only a few papers on the plasma diagnostics of atmospheric DBDs, but to the best of our knowledge, there are no detailed investiga- tions on low-pressure DBDs, such as those used for the analysis of halogenated hydrocarbons.