Berlin 2005 – scientific programme

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MO: Molekülphysik

MO 42: Poster II

MO 42.23: Poster

Tuesday, March 8, 2005, 14:00–16:00, Poster HU

Absolute measurements of amount of substance fractions by laser spectroscopy — •Jorge Koelliker Delgado, Olav Werhahn, and Detlef Schiel — Physikalisch-Technische Bundesanstalt, Bundesallee 100, D-38116 Braunschweig

Absolute measurement of amount of substance fractions (without calibration with the substance being measured) could be attractive due to its potential reduction of maintenance costs for spectrometric detection systems. Due to the impact of new QCL laser sources in the MIR laser-based gas analysis gains more attention. The feasibility of such a method has been studied with a test-system operating at wavelengths around 2.004 micrometer. Results on measuring mixtures of carbon dioxide in nitrogen will be presented. The gas mixtures were gravimetrically prepared. The relative deviation of the spectroscopic determination of the amount of substance fractions from the gravimetric values was measured. to be within 1 % . Traceable measurement results to SI and an uncertainty budget according to GUM are presented. The uncertainty budget reveals the main contribution originating from the line strength S. Values for this input quantity could be obtained from HITRAN database, e.g. for the selected absorption transition with a HITRAN claimed uncertainty between 2 and 5 % . With that given, the amount of substance measurement by laser spectroscopy features results with a total relative uncertainty of 4 % . The agreement with the gravimetric values is satisfactory and could render unbiased measurement results. Applications for exhaust gas emission calibration mixtures and CO2-in-room-air are presented.