共查询到20条相似文献,搜索用时 15 毫秒
1.
H. Dahnke J. Kahl G. Schüler W. Boland W. Urban F. Kühnemann 《Applied physics. B, Lasers and optics》2000,70(2):275-280
Isoprene (C5H8) is one of the most important biogenic volatile organic compounds (VOCs) in the atmosphere. To calculate the impact of isoprene
on atmospheric processes models have been developed that describe the isoprene release from plants. Measurements of this release
require techniques for a fast, sensitive, on-line isoprene detection.
Photoacoustic (PA) spectroscopy is applied here for the first time to monitor biogenic isoprene emissions. A CO overtone PA
spectrometer is used for the detection, probing the C-H stretching vibrations in the 3 to 4 μm range. This allows us to detect
isoprene down to a few ppb with a time resolution of one minute in a continuous gas flow. The number of laser lines can be
adjusted to meet the requirements of the respective experiment in terms of time resolution and selectivity against other possibly
interfering VOCs. This results in a highly versatile instrument for the isoprene detection in biological experiments. Furthermore,
the infrared fingerprint offers the potential to detect different isoprene isotopomers simultaneously, thus allowing us to
carry out on-line labelling experiments. The new apparatus was used to study the light dependence of isoprene emission from
Eucalyptus globulus. The results demonstrate, that the detector system is a promising tool for the study of plant gas emissions. It allows the
validation of existing emission models which are important for atmospheric processes.
Received: 18 March 1999 / Revised version: 23 August 1999 / Published online: 30 November 1999 相似文献
2.
M.B. Pushkarsky M.E. Webber O. Baghdassarian L.R. Narasimhan C.K.N. Patel 《Applied physics. B, Lasers and optics》2002,75(2-3):391-396
An industrial trace-ammonia sensor based on photoacoustic spectroscopy and CO2 lasers has been developed for measuring ammonia with a 1σ detection limit of 220 parts-per-trillion (ppt) in an integration
time of 30 s. The instrument response time for measuring ammonia was 200 s, limited by adsorption effects due to the polar
nature of ammonia. The minimum detectable fractional absorbance was 2.0×10-7, and the minimum normalized detectable absorption coefficient for this system was 2.4×10-7 W cm-1/z. The 9R(30) transition of the CO2 laser at 9.22 μm with 2 W of output power was used to probe the strong sR(5,K) multiplet of ammonia at the same wavelength. This sensor was demonstrated with an optically multiplexed configuration
for simultaneous measurement in four cells.
Received: 3 April 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-310/458-0171, E-mail: webber@pranalytica.com 相似文献
3.
A. Boschetti D. Bassi E. Iacob S. Iannotta L. Ricci M. Scotoni 《Applied physics. B, Lasers and optics》2002,74(3):273-278
A compact multi-component trace-gas detector based on the resonant photoacoustic technique and a NIR external cavity diode
laser has been developed. It has been characterized using a mixture of ethylene and methane diluted in ambient air. A spectroscopic
investigation of combination bands and overtones between 5900 and 6250 cm-1, obtained with an IR pulsed laser photoacoustic spectrometer, allowed us to find a wavelength region where the 2ν3 overtone of CH4 and the ν5+ν9 combination band of C2H4 show uncongested rotational lines. Using a single-mode scan of the diode laser in this region, around 6150 cm-1, the sensitivity for the simultaneous detection of ethylene and methane is 8 ppm/mW and 40 ppm/mW respectively. Factors affecting
the sensitivity and selectivity of the detection system and possible improvements suitable to reach the sub-ppm detection
limit are discussed.
Received: 1 August 2001 / Revised version: 28 November 2001 / Published online: 7 February 2002
An erratum to this article is available at . 相似文献
4.
F. Kühnemann M. Wolfertz S. Arnold M. Lagemann A. Popp G. Schüler A. Jux W. Boland 《Applied physics. B, Lasers and optics》2002,75(2-3):397-403
A photoacoustic spectrometer for the simultaneous detection of isoprene and the deuterated species [4,4-2H]-2-methyl-1,3-butadiene (isoprene-d2) is presented. Using a sealed-off 13CO2 laser a single-component detection limit of 400 ppt (isoprene) and 600 ppt (isoprene-d2) was achieved. Simultaneous monitoring of both compounds allowed the detection of labelling levels down to 6% (isoprene-d2 in total isoprene) with a time resolution of 3 min.
In emission studies with Eucalyptus globulus, the deuterated precursor [4,4-2H]-1-deoxy-D-xylulose was fed to a leaf through the transpiration stream. Emission of isoprene-d2 started as early as 10 min after application of the precursor.
Received: 3 May 2002 / Revised version: 31 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-228/733474, E-mail: frank.kuehnemann@iap.uni-bonn.de 相似文献
5.
Z. Bozóki J. Sneider G. Szabó A. Miklós M. Serényi G. Nagy M. Fehér 《Applied physics. B, Lasers and optics》1996,63(4):399-401
The first use of an external cavity diode-laser light source in combination with a photoacoustic detector for high-sensitivity gas detection is described. This combined system is applicable for detecting gases with absorption coefficients as low as 5 x 10–8 cm–1 by operating the photoacoustic cell in an intracavity mode. Measurements were made on the 1.13 m absorption lines of water vapour. For quantitative measurements, it was found to be necessary to introduce a reference cell into the system. 相似文献
6.
F. Kühnemann K. Schneider A. Hecker A.A.E. Martis W. Urban S. Schiller J. Mlynek 《Applied physics. B, Lasers and optics》1998,66(6):741-745
2 H6) at 3.34 μm using a widely tunable cw single-frequency optical parametric oscillator. The high frequency and power stability
and the continuous tunability of the parametric oscillator make it ideally suited for this application. Detection sensitivities
of 0.5 ppb for ethane are obtained, which is comparable to the best results previously obtained with intracavity detection
using line-tunable CO overtone lasers. The flexibility and compact size of cw single-frequency parametric oscillators can
lead to portable photoacoustic trace-gas detection systems for environmental monitoring and process control.
Received: 28 January 1998/Revised version: 9 April 1998 相似文献
7.
A dual-beam laser absorption spectrometer with balanced detection for high sensitivity detection of oxygen via the A-band
at 760 nm is described. The 2×2 vertical-cavity surface-emitting laser arrays used for this set-up are characterized by their
wavelength tuning behavior with temperature and current, amplitude modulation, side-mode suppression ratio and polarization
contrast. The spectrometer performance is determined over time periods of up to 10 h using the variation in the differential
absorption between two beam paths. With the R11R11 line at STP, 670 μW laser power and 200 mm-long absorption cells, we realized
an excellent linearity (R=0.9999) and over a 5-min interval a record sensitivity for VCSEL-based spectrometers of 35 ppmV,
corresponding to an optical density (O.D.) of 7×10-7. For this specific set-up, this sensitivity is only a factor of 2.7 above the shot noise limit, giving us a normalized detection
limit of 7.6 ppmV·m·. Over a 10-h interval we achieved a standard deviation of 65 ppmV.
Received: 26 July 2000 / Revised version: 1 November 2000 / Published online: 6 December 2000 相似文献
8.
Wavelength modulation, diode laser atomic absorption spectrometry is applied to measure traces of argon and krypton in other
noble gases. Strong transitions from long-lived metastable levels highly populated in a low-pressure dc discharge are induced
with a standard diode laser in the spectral range around 811 nm. The detection limits achieved are in the lower ppbv range,
and the residual concentrations of Kr and Ar traces in the utilized high-purity noble gases are measured.
Received: 2 October 2000 / Final version: 3 May 2001 / Published online: 7 June 2001 相似文献
9.
G. Totschnig M. Lackner R. Shau M. Ortsiefer J. Rosskopf M.C. Amann F. Winter 《Applied physics. B, Lasers and optics》2003,76(5):603-608
A single-frequency VCSEL has been used for the first time for high-resolution spectroscopy near 1.5 μm. The incorporated buried-tunnel-junction
technology enabled the realization of a long-wavelength InGaAlAs/InP VCSEL with low threshold current (0.925 mA), high output
powers (0.576 mW) and low series resistance (60 Ω). The high-speed tuning capability of the long-wavelength VCSEL was investigated
and used to conduct high-speed absorption spectroscopy. The peak tuning speed was measured to be 3.4 cm-1/μs and a 4.5-cm-1-wide NH3 spectrum was recorded in 2 μs. The VCSEL was used to measure highly resolved low-pressure spectra for pressures ranging from
9.6 mbar to 1 bar. The measured Doppler-broadened linewidth of 0.02 cm-1 agrees within 3% with the theoretical calculations. The availability and various advantages of 1.3–2-μm single-frequency
VCSELs as compared to edge-emitting diode lasers, such as a large current tuning range even at very high tuning frequencies,
and low production costs, should significantly expand the application fields for near-infrared laser gas sensors.
Received: 17 July 2002 / Revised version: 4 December 2002 / Published online: 12 May 2003
RID="*"
ID="*"Corresponding author. Fax: +43-1/58801-15999, E-mail: Gerhard@Totschnig.com 相似文献
10.
L. Menzel A.A. Kosterev R.F. Curl F.K. Tittel C. Gmachl F. Capasso D.L. Sivco J.N. Baillargeon A.L. Hutchinson A.Y. Cho W. Urban 《Applied physics. B, Lasers and optics》2001,72(7):859-863
Two configurations of a continuous wave quantum cascade distributed feedback laser-based gas sensor for the detection of NO
at a parts per billion (ppb) concentration level, typical of biomedical applications, have been investigated. The laser was
operated at liquid nitrogen temperature near λ=5.2 μm. In the first configuration, a 100 m optical path length multi-pass
cell was employed to enhance the NO absorption. In the second configuration, a technique based on cavity-enhanced spectroscopy
(CES) was utilized, with an effective path length of 670 m. Both sensors enabled simultaneous analysis of NO and CO2 concentrations in exhaled air. The minimum detectable NO concentration was found to be 3 ppb with a multi-pass cell and 16 ppb
when using CES. The two techniques are compared, and potential future developments are discussed.
Received: 1 November 2000 / Revised version: 19 January 2001 / Published online: 20 April 2001 相似文献
11.
D.D. Nelson J.H. Shorter J.B. McManus M.S. Zahniser 《Applied physics. B, Lasers and optics》2002,75(2-3):343-350
Non-cryogenic, laser-absorption spectroscopy in the mid-infrared has wide applications for practical detection of trace gases
in the atmosphere. We report measurements of nitric oxide in air with a detection limit less than 1 nmole/mole (<1 ppbv) using
a thermoelectrically cooled quantum cascade laser operated in pulsed mode at 5.26 μm and coupled to a 210-m path length multiple-pass
absorption cell at reduced pressure (50 Torr). The sensitivity of the system is enhanced by operating under pulsing conditions
which reduce the laser line width to 0.010 cm-1 (300 MHz) HWHM, and by normalizing pulse-to-pulse intensity variations with temporal gating on a single HgCdTe detector.
The system is demonstrated by detecting nitric oxide in outside air and comparing results to a conventional tunable diode
laser spectrometer sampling from a common inlet. A detection precision of 0.12 ppb Hz-1/2 is achieved with a liquid-nitrogen-cooled detector. This detection precision corresponds to an absorbance precision of 1×10-5 Hz-1/2 or an absorbance precision per unit path length of 5×10-10 cm-1 Hz-1/2. A precision of 0.3 ppb Hz-1/2 is obtained using a thermoelectrically cooled detector, which allows continuous unattended operation over extended time periods
with a totally cryogen-free instrument.
Received: 1 May 2002 / Revised version: 6 June 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-978/663-4918, E-mail: ddn@aerodyne.com 相似文献
12.
Portable difference-frequency laser-based cavity leak-out spectrometer for trace-gas analysis 总被引:1,自引:0,他引:1
We report a portable mid-infrared spectrometer for trace-gas analysis which is based on an all-solid-state difference-frequency-generation
laser. The spectrometer provides in situ absorption path lengths of more than 3 km by means of the cavity leak-out method,
a cw variant of the cavity ring-down technique. The design, performance, and application of this spectrometer are presented.
The light source utilizes difference-frequency generation in a periodically poled lithium niobate (PPLN) crystal pumped by
two single-frequency solid-state lasers. A maximum power of 27 μW in the wavelength region near 3.3 μm is achieved using a
pump power of 20 mW at 808 nm, a signal power of 660 mW at 1064 nm, and a 50-mm-long PPLN crystal. This corresponds to a conversion
efficiency of 0.42 mW/(W2 cm). We demonstrate that this portable laser system is suitable as a light source in a cavity leak-out spectrometer. We achieved
a minimum detectable absorption coefficient of 1×10-8/cm (integration time: 2 s), corresponding, for example, to a detection limit of 1 part per billion ethane. This compact trace-gas
analyzer with high sensitivity and specificity is promising for various environmental and medical applications.
Received: 8 April 2002 / Revised version: 28 May 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +49-211/811-3121, E-mail: muertz@uni-duesseldorf.de 相似文献
13.
Ultra-sensitive mid-infrared cavity leak-out spectroscopy using a cw optical parametric oscillator 总被引:1,自引:0,他引:1
A. Popp F. Müller F. Kühnemann S. Schiller G. von Basum H. Dahnke P. Hering M. Mürtz 《Applied physics. B, Lasers and optics》2002,75(6-7):751-754
We report a portable, all-solid-state, mid-infrared spectrometer for trace-gas analysis. The light source is a continuous-wave
optical parametric oscillator based on PPLN and pumped by a Nd:YAG laser at 1064 nm. The generated single-frequency idler
output covers the wavelength region between 2.35 and 3.75 μm. With its narrow line width, this light source is suitable for
precise trace-gas analysis with very high sensitivity. Using cavity leak-out spectroscopy we achieved a minimum detectable
absorption coefficient of 1.2×10-9 /cm (integration time: 16 s), corresponding, for example, to a detection limit of 300 parts per trillion ethane. This sensitivity
and the compact design make this trace-gas analyzer a promising tool for various in situ environmental and medical applications.
Received: 19 September 2002 / Published online: 15 November 2002
RID="*"
ID="*"Corresponding author. Fax: +49-228/733-474, E-mail: frank.kuehnemann@iap.uni-bonn.de 相似文献
14.
H. Du J. W. Fang G. J. Chen T. Q. Cai J. J. Zheng 《Applied physics. B, Lasers and optics》1997,64(3):377-381
An experimental method to study the photochemical reaction in solid-state dichromated gelatin during exposure is proposed,
in which two laser sources with different wavelengths are used to induce photoreaction and to excite photoacoustic signal,
respectively. This method is to obtain the real-time characteristics during the formation of the photoreaction product. The
curve is fitted using the Rosencwaig-Gersho (R-G) theory and chemical kinetics. The reaction order and the rate of reaction
may be obtained by fitting the parameters. The results show that photochemical reaction in dichromated gelatin conforms to
the mechanism suggested by Watanable-Westheimer, and the photosensitivity of the samples, prepared under different conditions,
is dependent on the initial concentration of photoactive ions.
Received: 18 April 1995/Revised version: 3 May 1996 相似文献
15.
An all-diode-laser-based spectrometer is used for the simultaneous detection of methane, oxygen and water vapour. This is
accomplished using a 760-nm diode laser and a 980-nm diode laser in conjunction with difference-frequency generation to 3.4 μm
in a periodically poled lithium niobate crystal. Each of the output wavelengths is resonant with one of the molecular species.
Simultaneous recordings over a 15-m open path of laboratory air are demonstrated. The recording scheme shows the wide applicability
of a diode-laser-based difference-frequency spectrometer for the detection of molecular species in different wavelength ranges.
By increasing the frequency of the 760-nm diode laser and decreasing the frequency of the 980-nm diode laser, a maximum continuous
tuning range in the mid infrared of 3.6 cm-1 is achieved. This enables the recording of several methane lines at atmospheric pressure. Pressure-dependence studies of
methane lineshapes are also performed in an absorption cell. An indoor-air methane background level of 3 ppm is measured.
The signal-to-noise ratio in the recorded methane spectra indicates that sub-ppm detection of methane at atmospheric pressure
is feasible.
Received: 6 March 2000 / Revised version: 19 June 2000 / Published online: 11 October 2000 相似文献
16.
Kosterev AA Tittel FK Durante W Allen M Kohler R Gmachl C Capasso F Sivco DL Cho AY 《Applied physics. B, Lasers and optics》2002,74(1):95-99
We report the first application of pulsed, near-room-temperature quantum cascade laser technology to the continuous detection
of biogenic CO production rates above viable cultures of vascular smooth muscle cells. A computer-controlled sequence of measurements
over a 9-h period was obtained, resulting in a minimum detectable CO production of 20 ppb in a 1-m optical path above a standard
cell-culture flask. Data-processing procedures for real-time monitoring of both biogenic and ambient atmospheric CO concentrations
are described.
Received: 24 October 2001 / Published online: 29 November 2001 相似文献
17.
2 monitor designed for field applications using room-temperature diode lasers are presented. Near-infrared DFB lasers operating
at 1.57 μm and around 2.0 μm have been used for CO2 measurements. At ambient concentration levels a resolution of more than two orders of magnitude has been demonstrated at
1.57 μm, at 2 μm the precision is in the order of 0.1 ppm CO2, and for trace analysis a detection limit of 10 ppb has been obtained. The measurements demonstrate the capability of near-infrared
DFB diode lasers for the precise determination of CO2 concentrations as required for climatological, medical, or industrial applications.
Received: 24 February 1998/Revised version: 27 April 1998 相似文献
18.
Kosterev AA Curl RF Tittel FK Rochat M Beck M Hofstetter D Faist J 《Applied physics. B, Lasers and optics》2002,75(2-3):351-357
Pulsed thermoelectrically cooled QC-DFB lasers operating at 15.6 μm were characterized for spectroscopic gas sensing applications.
A new method for wavelength scanning based on repetition rate modulation was developed. A non-wavelength-selective pyroelectric
detector was incorporated in the sensor configuration giving the advantage of room-temperature operation and low cost. Absorption
lines of CO2 and H2O were observed in ambient air, providing information about the concentration of these species.
Received: 29 April 2002 / Published online: 21 August 2002
RID="*"
ID="*"Corresponding author. Fax: +1-713/348-5686, E-mail: akoster@rice.edu 相似文献
19.
By optically pumping the deuterated isotopomers of 14NH3 and 15NH3 using 12C16O2, 13C16O2, 12C18O2, and 13C18O2 lasers, several new far-infrared (FIR) emission lines between 65 μm and 125 μm have been detected. The existing spectroscopy
of 14N-ammonia isotopomers has been used to identify many of these lines, as well as some previously observed but unidentified.
The spectroscopic data have been analyzed to predict over 20 additional FIR laser lines that could be pumped by a more capable
CO2 laser. This effort was motivated by a need for strong laser lines in frequency coincidence with molecular transitions of
astrophysical interest. Of particularnote is the measurement of the 2680-GHz line of 14NHD2, whose frequency is 4.9 GHz higher than that of the important J=1-0 line of interstellar HD.
Received: 25 July 2002 / Published online: 20 December 2002
RID="*"
ID="*"Corresponding author. Fax: +1-303/492-5941, E-mail: boreiko@spot.colorado.edu 相似文献
20.
G. Modugno C. Corsi M. Gabrysch F. Marin M. Inguscio 《Applied physics. B, Lasers and optics》1998,67(3):289-296
2 , and its sensitivity is 7(2)×10-8 in a 1-Hz bandwidth. The corresponding minimum detectable concentration of CO2 in air has been estimated to be 1 ppm · m. This opens the possibility of a detection at ppb levels at 2 μm, where a two orders
of magnitude increase in the CO2 absorption signal is demonstrated.
Received: 06 April 1998/Revised version: 02 July 1998 相似文献