Berlin 2012 – wissenschaftliches Programm
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UP: Fachverband Umweltphysik
UP 9: Poster session
UP 9.15: Poster
Mittwoch, 28. März 2012, 18:30–19:15, Poster F
Detection of CO and N2O in the exhaust of a combustion engine with a continuous wave, room temperature distributed-feedback quantum cascade laser — •Florian Schad1, Wolfgang Elsäßer1,2, and Andreas Dreizler2 — 1TU Darmstadt, Institut für Angewandte Physik — 2TU Darmstadt, Exzellenzcluster Center of Smart Interfaces
Carbon monoxide (CO) is a highly toxic trace gas in earth’s atmosphere. It is a major pollutant which arises from incomplete combustion processes and is therefore an important indicator of combustion efficiency in the exhaust of cars. The concentration level of nitrous oxide (N2O) in the exhaust gas is much lower than that of CO but recent investigations show an increased output of N2O if three-way catalysts are used. To measure these molecules, we realized a sensor based on a cw, room temperature DFB quantum cascade laser (QCL) emitting at 4.56 µm. Around that wavelength are the fundamental transitions of CO and N2O, with its high absorption line strengths, located.
We first present direct absorption measurements of the CO and N2O sensor performed on gas samples in a 10 cm cell. Due to the calibration-free method, the respective concentrations were directly calculated based on data of the HITRAN data base. The liquid-nitrogen cooled MCT-Detector guarantees for highly sensitive measurements, which results in a detection limit below 20 ppm. Then wavelength modulation spectroscopy results of N2O are discussed with a detection limit of about 30 ppb. With this sensor concept we intend to measure the CO and N2O concentrations directly in the exhaust of a diesel engine.