Sensitive intracavity photoacoustic measurements with a CO2 waveguide laser

Harren, F.J.M.; Bijnen, F.G.C.; Reuß, J.; Voesenek, L.A.C.J.; Blom, C.W.P.M.

doi:10.1007/bf00331909

Cited by 158 publications

(97 citation statements)

References 21 publications

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“…This observed relatively slow final decay of the signal was probably caused by the fact that the buffer volumes at the outlet of the PA cell were not sufficiently diluted by additional buffer flows (Harren et al 1990). Measuring high concentrations of CH, or DMS over long time periods results in accumulation of high concentrations in the buffer volume.…”

Section: Resultsmentioning

confidence: 99%

“…Photoacoustics, on the other hand, is restricted to the measurement of relatively small molecules having an absorption in the wavelength range of the laser used. Practical laser sources for photoacoustic trace gas detection are the CO* laser (9-l 1 pm wavelength region) (Harren et al, 1990) the AV=l CO laser (4.8-7.8 urn) (Bijnen, 1995;Bijnen et al, 1995;1996) and the AV=2 CO laser (2.5-3.8 urn) (Bachem et al, 1993). Our results show that with the AV=l CO laser not only CH4, but also other gaseous compounds such as DMS and TMA can principally be measured, if the configuration of the diffusion probe is further improved.…”

Section: Discussionmentioning

confidence: 99%

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Combination of photoacoustic detector with gas diffusion probes for the measurement of methane concentration gradients in submerged paddy soil

Rothfuß¹,

Bijnen²,

Conrad³

et al. 1997

Atmospheric Environment

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Dissolved methane was monitored by means of a diffusion probe in combination with a photoacoustic (PA) detector cell placed in the cavity of a liquid nitrogen-cooled CO laser. The detection limit of the photoacoustic detector was 1 ppbv methane (= 2 uM in aqueous solution), the time response was 60 s, the spatial resolution was 1.36 mm. These limits were determined by the acoustic noise and the configuration of the diffusion probe. The combination of PA detector with gas diffusion probes was found to be useful for monitoring gaseous compounds. However, the membrane material of the diffusion probe was critical. Silicone as membrane material was useful only for measurement of CH4. Goretex as membrane material was applicable to measurement of dimethylsulfide (DMS), but did not give a stable signal for trimethylamine (TMA).Vertical concentration profiles of CH4 in anoxic paddy soil agreed well with earlier results obtained with a gas chromatograph as detector. Methane was produced in anoxic soil layers below 8-l 0 mm depth and diffused upwards to the surface through a layer of CH4-consuming bacteria situated at about 2 mm depth. In the oxic upper 2 mm soil layer the concentration of CH4 decreased below the detection limit of our system. Methane-containing gas bubbles that were embedded in the soil were detected by a steep increase of the CH4 signal. The combination of PA detector and gas diffusion probe was found to be a useful tool to measure CH4 gradients in submerged soil or sediment with high temporal and spatial resolution, thus allowing the localization and quantification of CH4 production and CH4 oxidation rates within the soil profile.

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Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Combination of photoacoustic detector with gas diffusion probes for the measurement of methane concentration gradients in submerged paddy soil

Rothfuß¹,

Bijnen²,

Conrad³

et al. 1997

Atmospheric Environment

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“…1) with an intracavity waist of 280/tm, produced between an intracavity lens 0" = 75 mm) and the curved output mirror (radius of curvature 270mm, reflection of 98.50/0). (14) In this way a high local intensity is achieved producing a well-defined heated region where the probe laser passes over the pump beam. To ot.…”

Section: Photothermal Detection Of Gasesmentioning

confidence: 99%

IR laser photothermal trace gas detection applied to environmental and biological problems

Vries¹,

Lieshout²,

Harren³

et al. 1995

Infrared Physics & Technology

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Please be advised that this information was generated on 2018-05-09 and may be subject to change. Per a.o.Inl 'rared Phys. Technol. Vol. 36, No. I, pp. 483488, 1995 Copyright '7 1995 Elsevier Science Ltd 1350 A~tract--The photothermal effect is utilized for the detection of molecular trace gases in the open air, with high spatial and temporal resolution. An IR CO 2 laser is used to excite specific molecules to higher vibrational levels. The subsequent change in temperature and refractive index is monitored by the deflection of a HeNe laser beam which crosses the CO 2 laser beam. To improve the detection limit of the system the CO, laser has an intracavity focus near to which the HeNe laser passes 31 times in a multipass mirror setup. A detection sensitivity of I ppbv (C2H4) and 0.5 ppbv (NH3) is achieved under practical conditions.

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“…Sigrist ( ) Laser Spectroscopy and Sensing Laboratory, Institute of Quantum Electronics, ETH Zurich, Schafmattstr. 16, 8093 Zurich, Switzerland e-mail: sigrist@iqe.phys.ethz.ch Fax: +41- for photoacoustic cells have been proposed: acoustically resonant [4][5][6][7][8][9][10], multipass [11,12], intracavity [13,14], parallel [15], "windowless" [16], differential [17] and quartz enhanced [18]. In most known photoacoustic sensing schemes, the absolute values of the microphone signal are measured and used to derive the concentration of the gas of interest ( [3] and references therein).…”

Section: Introductionmentioning

confidence: 99%

Near-infrared resonant photoacoustic gas measurement using simultaneous dual-frequency excitation

et al. 2010

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The simultaneous dual-frequency operation of a resonant photoacoustic gas sensor based on the differential mode excitation photoacoustic (DME-PA) technique is presented. The DME-PA method uses the excitation of two different modes in a resonant photoacoustic cell and the gas concentration is derived from the amplitude ratio of these acoustic modes. With the simultaneous dual-frequency excitation, the amplitude ratio needed by the DME-PA technique is obtained instantaneously, in contrast to the sequential modulation scheme where additional time delays are introduced by changing the modulation frequency. For a given excitation power reaching the photoacoustic cell, and a total acquisition time longer than 7 s, the simultaneous modulation scheme provides an improved measurement uncertainty compared to the sequential scheme. The proposed sensor allows measuring water vapour with a ±150 ppmV uncertainty using current-modulated near-infrared LEDs and a 15 s total acquisition time.

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Sensitive intracavity photoacoustic measurements with a CO2 waveguide laser

Cited by 158 publications

References 21 publications

Combination of photoacoustic detector with gas diffusion probes for the measurement of methane concentration gradients in submerged paddy soil

Combination of photoacoustic detector with gas diffusion probes for the measurement of methane concentration gradients in submerged paddy soil

IR laser photothermal trace gas detection applied to environmental and biological problems

Near-infrared resonant photoacoustic gas measurement using simultaneous dual-frequency excitation

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