Monitoring of Gaseous Pollutants by Tunable Diode Lasers

In 1986, an International Symposium on Monitoring of Gaseous Pollut ants by Tunable Diode Lasers was organized by the Fraunhofer-Institut fuer Physikalische Messtechnik in Freiburg, FRG, and held at this institution on November 13-14, 1986. The papers presented at that occasion extensively covered the applications of tunable diode laser spectroscopy (TDLS) to the analysis of trace and exhaust gases together with the latest improvements brought to the tech niques used. It was generally consented by the participants that meetings of this kind are of major importance and should take place on a regular basis. The organizers were thus encouraged to plan a Second International Sympo sium on Monitoring of Gaseous Pollutants by Tunable Diode Lasers which was held two years later on October 17-18, 1988, again in Freiburg. In addi tion to the main subjects treated in the first Symposium, the Scientific Programme this time presented a session on the development of lead chalco genide lasers. Once more, only a limited attention was given to applica tions in high resolution molecular spectroscopy. In order to complete the update, sessions on components and techniques were included in the Pro gramme. As for the previous Symposium, some space was also given to alter native optical techniques. This time, in particular contributions on laser photoacoustic detection were included.

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Monitoring of Gaseous Pollutants by Tunable Diode Lasers is divided into four sections: I -- Atmospheric Trace Gas Detection; II -- Diode Lasers and Their Properties, including Progress in IV-VI Physics and Optoelectronic Devices; III -- Techniques, Systems, Components; IV - Special Applications. Atmospheric trace gas detection was of central interest, and the presentations clearly demonstrate the impressive capabilities of the diode laser technique. Reports on IV-VI mid-infrared diode lasers stress those properties -- radiation noise and emission linewidth -- which are essential for application to ultra-high sensitivity pollution monitoring. Two reports on III-V systems emitting at wavelengths shorter than 3 mum show that the less severe cooling requirements can lead to more compact equipment which can be used to detect pollutants via overtone absorption bands. The presentations on IV-VI physics and devices stress the physical and technological aspects of mid-infrared diode lasers. Laterally structured diode lasers are discussed in detail. There is also extensive material which compares traditional AM and the more recent FM techniques. The reports on special applications point to new directions for research, thus rounding off a complete, expert discussion of a vital research area.

Contenu
I. Atmospheric Trace Gas and Exhaust Gas Analysis.- Long-path diode laser measurement of industrial air pollution.- Measurements of atmospheric HCl and NH3 with a mobile tunable diode laser system.- Atmospheric trace gas measurement on the Schauinsland surveying station.- Tunable diode laser absorption spectrometry as a reference method for tropospheric measurements.- Functional testing of a multicomponent diode laser spectrometer (DIOLA) in comparison with the conventional technology.- Dynamic car exhaust gas analysis using tunable IR diode lasers.- Measurement of trace species in the remote maritime boundary layer using TDLAS.- II. Lead Chalcogenide Diode Laser Development.- Development of lead chalcogenide lasers at Fujitsu.- Status of lead salt diode laser development at Spectra Physics.- Recent results in lead-salt laser development at the IPM.- III. Components and Techniques.- High frequency modulation spectroscopy with a lead salt diode laser.- Current status of frequency calibration tables (0 to 3000 cm?1) for tunable diode lasers from heterodyne frequency measurements.- Oxygen measurement with GaAlAs diode lasers.- Absorption spectrometry for atmospheric methane:techniques for higher sensitivity..- Computer controlled diode laser spectrometer.- An anastigmatic White cell for IR diode laser spectroscopy.- CO-laser-magnetic-resonance facility for sensitive detection of radical trace gases (NOX, HO2?).- High-sensitivity frequency modulation spectroscopy with lead-salt diode lasers..- On the adsorption properties of ammonia to various surfaces.- IV. Special Applications.- Application of tunable diode lasers to laboratory studies of atmospheric chemistry: kinetics of the reaction NO3+NO2 --> NO+NO2+O2.- Monitoring of metal oxides in low pressure flames.- Diodelaser spectroscopy of transient species in electric discharges.- Diode laser application for measurements of foreign-gas broadening of v2 band in NH3.- Carbon monoxide concentrations and temperature measurements in combustion gases.- V. Photoacoustics.- Line strength measurement using optoacoustic spectroscopy.- A novel wide temperature range photoacoustic cell for molecules in the vapour phase.- Photoacoustic investigation of pesticides.- Sensitive photoacoustic trace detection of ethylene.- Photoacoustic detection of ethylene evolution in emasculated Cymbidium and Oncidium orchid flowers..- List of Participants.- Index of Authors.