共查询到20条相似文献,搜索用时 31 毫秒
1.
We present measurements of the net-induced gain on the 5d–4f transition at 186 nm in LiYF4 : Nd3+ optically pumped by radiation from a molecular fluorine laser. It is found that for LiYF4 : Nd3+, one of a series of potential continuously tunable VUV lasers, relatively strong excited-state absorption results in net-induced
loss. The prospects for VUV laser operation being realised in other rare-earth-doped fluorides is discussed.
Received: 4 March 1996/Revised version: 10 July 1996 相似文献
2.
I. Ventrillard-Courtillot E. Sciamma O’Brien S. Kassi G. Méjean D. Romanini 《Applied physics. B, Lasers and optics》2010,101(3):661-669
In the past decade, due to a growing awareness of the importance of air quality and air pollution control, many diagnostic
tools and techniques have been developed to detect and quantify the concentration of pollutants such as NO
x
, SO
x
, CO, and CO2. We present here an Incoherent Broad-Band Cavity-Enhanced Spectroscopy (IBB-CEAS) set-up which uses a LED emitting around
625 nm for the simultaneous detection of NO2 and NO3. The LED light transmitted through a high-finesse optical cavity filled with a gas sample is detected by a low resolution
spectrometer. After calibration of the spectrometer with a NO2 reference sample, a linear multicomponent fit analysis of the absorption spectra allows for simultaneous measurements of
NO2 and NO3 concentrations in a flow of ambient air. The optimal averaging time is found to be on the order of 400 s and appears to be
limited by the drift of the spectrometer. At this averaging time the smallest detectable absorption is 2×10−10 cm−1, which corresponds to detection limits of 600 pptv for NO2 and 2 pptv for NO3. This compact and low cost instrument is a promising diagnostic tool for air quality control in urban environments. 相似文献
3.
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
4.
F. Assenmacher M. Gutmann F. Noack V. Stert W. Radloff 《Applied physics. B, Lasers and optics》2000,71(3):385-390
The photodissociation dynamics of HNO3 in the electronic S3 (2 1
A
′
) state leading to the fragments OH and NO2 was investigated in real time. HNO3 was prepared either in a fluorescence cell at room temperature (LIF probing of OH) or rotationally cold in a molecular beam
(probing of NO2 by three-photon ionization). A 2 1
A
′
lifetime of 60–80 fs could be obtained from the experimental results, indicating essentially barrierless dissociation. In
addition, secondary dissociation of internally excited nascent fragments NO2
* leading to products NO(X 2
Π) and O(3
P) with a characteristic dissociation time of 2.3 ps was observed. This time is surprisingly long when compared with dissociation
lifetimes of NO2 from the literature, obtained after direct photoexcitation. The discrepancy is explained by differences in the preparation
conditions of the dissociative state of NO2.
Received: 12 November 1999 / Published online: 13 July 2000 相似文献
5.
A detection limit of 200 ppt of NO2 in N2 at atmospheric pressure was obtained with a photoacoustic detector and a high power blue laser diode. This corresponds to
a normalized noise (1σ) equivalent absorption coefficient of 2×10-9 cm-1W/Hz0.5. Measurements at different laser modulation frequencies showed no frequency dependence of the photoacoustic signal, indicating
a relaxation time τ < 4 μs. Mixing O2 into the NO2 containing gas results in a decrease of the photoacoustic signal. A simple model shows that this effect can be attributed
to an increased vibrational-vibrational relaxation of NO2 to O2.
PACS 31.70.Hq; 34.50.Ez; 42.55.Px 相似文献
6.
Incorporation of phosphorus into silicon from a spin-on dopant layer (SOD) at 400 °C is described.
Annealing experiments were carried out with SOD films deposited on (100) silicon substrates by using the spin-on technique.
Conventional heating on a hotplate in normal atmosphere and a temperature range up to 400 °C was used to study the dopant incorporation. After removing the SOD-films one part of the silicon substrates was annealed
at higher temperatures. Investigations were carried out by SIMS, SAM, XPS, HTEM, stripping Hall and Van der Pauw measurements
before and after the high temperature annealing.
Chemical phosphorus concentration profiles obtained from low temperature annealed samples showed diffusion depths of 60–80 nm
(extrapolated to a substrate doping level of 1016 cm-3) and surface concentrations of 1019–1020 cm-3. Electron concentration profiles exhibiting maximum values around 2⋅1019 cm-3 could be measured on high temperature annealed samples only.
Received: 28 March 1996/Accepted: 19 August 1996 相似文献
7.
Gain versus tuning issues to Q-switch with Yb<Superscript>3+</Superscript>:LSO and amplify broad-bandwidth pulses 总被引:1,自引:0,他引:1
We report on the development of Incoherent Broadband Cavity Enhanced Absorption Spectroscopy (IBBCEAS) using a blue light
emitting diode (LED) for the detection of NO2 in laboratory ambient air. Absorption of the oxygen collisional pair in the atmosphere was also detected in the same spectral
range. The mirror reflectivity was determined using a standard gas sample mixture of NO2, and calibrated with the help of the absorption spectrum of the oxygen collisional pair in pure oxygen at atmospheric pressure.
Optimization of the experimental parameters was investigated and is discussed in detail. For the first time in IBBCEAS involving
broadband absorption spectra, averaging time for signal-to-noise ratio enhancement has been optimized using Allan variance
plot. 18.1 ppbv NO2 in laboratory ambient air has been retrieved from the absorption spectra using differential fitting method over a 40 nm spectral
region centered at 470 nm. A minimum detection sensitivity of about 2.2 ppbv (1σ) for NO2 at atmospheric pressure has been achieved using the optimal averaging time of 100 s by means of a high finesse optical cavity
formed with two moderate reflectivity (∼99.55%) mirrors. No purging of the cavity mirrors by high purity He or N2 gas streams was necessary to prevent contamination of the mirror faces for the in situ measurements. 相似文献
8.
L. Ciaffoni B. L. Cummings W. Denzer R. Peverall S. R. Procter G. A. D. Ritchie 《Applied physics. B, Lasers and optics》2008,92(4):627-633
High resolution diode laser spectroscopy has been applied to the detection of hydrogen sulphide at ppm levels utilizing different
transitions within the region of the ν
1+ν
2+ν
3 and 2ν
1+ν
2 combination bands around 1.58 μm. Suitable lines in this spectral region have been identified, and absolute absorption cross
sections have been determined through single-pass absorption spectroscopy and confirmed in the Doppler linewidth regime using
cavity enhanced absorption spectroscopy (CEAS). The desire for a sensitive system potentially applicable to H2S sensing at atmospheric pressure has led to an investigation on suitable transitions using wavelength modulation spectroscopy
(WMS). The set-up sensitivity has been calculated as 1.73×10−8 cm−1 s1/2, and probing the strongest line at 1576.29 nm a minimum detectable concentration of 700 ppb under atmospheric conditions
has been achieved. Furthermore, pressure broadening coefficients for a variety of buffer gasses have been measured and correlated
to the intermolecular potentials governing the collision process; the H2S–H2S dimer well depth is estimated to be 7.06±0.09 kJ mol−1. 相似文献
9.
J. Luque J.B. Jeffries G.P. Smith D.R. Crosley 《Applied physics. B, Lasers and optics》2001,73(7):731-738
The combination of two-dimensional, planar laser-induced fluorescence (PLIF) and cavity ring-down (CRD) absorption spectroscopy
is applied to map quantitatively the spatial distributions of CH2O and CH in a methane/air flame at 25 Torr. Both species are detected in the same spectral region using the overlapping CH2O A 1
A
2
-X
1
A
1
41
0 and CH B-X(1,0 )bands. The combination of diagnostic techniques exploits the spatial resolution of LIF and the quantitative
CRD absorption measure of column density. The spatially resolved PLIF provides the distribution of absorbers and line-of-sight
CRD absorption the absolute number density needed for quantitative concentration images. The peak CH2O concentration is (3.5±1.4 )×1014 cm-3, or 1450±550 ppm at 1000 K. The lack of precise absorption cross-section data produces these large error limits. Although
a flame model predicts lower amounts, these large uncertainties limit this measurement’susefulness as a test of the flame
chemistry.
Received: 24 April 2001 / Revised version: 10 July 2001 / Published online: 10 October 2001 相似文献
10.
Water-soluble Mn2+-doped ZnS quantum dots (QDs) were prepared using mercaptoacetic acid as the stabilizer. The optical properties and structure
features were characterized by X-Ray, absorption spectrum, IR spectrum and fluorescence spectrum. In pH 7.8 Tris-HCl buffer,
the QDs emitted strong fluorescence peaked at 590 nm with excitation wavelength at 300 nm. The presence of sulfide anion resulted
in the quenching of fluorescence and the intensity decrease was proportional to the S2− concentration. The linear range was from 2.5 × 10−6 to 3.8 × 10−5 mol L−1 with detection limit as 1.5 × 10−7 mol L−1. Most anions such as F−, Cl−, Br−, I−, CH3CO2
−, ClO4
−, CO3
2−, NO2
−, NO3
−, S2O3
2−, SO3
2− and SO4
2− did not interfere with the determination. Thus a highly selective assay was proposed and applied to the determination of
S2− in discharged water with the recovery of ca. 103%. 相似文献
11.
T. Yu Y.-F. Chen Z.-G. Liu L. Sun S.-B. Xiong N.-B. Ming Z.-M. Ji J. Zhou 《Applied Physics A: Materials Science & Processing》1996,64(1):69-72
The semiconductive perovskite-type oxide SrFeO3-x (x<0.16) (SFO) thin films have been directly fabricated on (001)SrTiO3 and (001)LaAlO3 single crystal substrates by pulsed laser deposition(PLD) under high oxygen partial pressure of 100 Pa. The SFO thin films
were (110) oriented. The x-ray photoelectron spectroscopy (XPS) analysis showed that the surface of SFO thin film has strong
gas absorption capability. The resistance versus temperature has been measured in the temperature range from 77 K to 300 K.
The SFO thin film showed typical semiconductive property. Dependence of resistance of SFO thin film on oxygen pressure was
measured and result showed that the SFO thin film had better oxygen sensitive property.
Received: 14 May 1996/Accepted: 15 August 1996 相似文献
12.
A new anthracene-based fluorescent PET sensor 1 with a tridentate ionophore of amide/β-amino alcohol displays very good selectivity and sensitivity for Fe3+ (K
a = 1.6 × 103 M−1) and Hg2+ (K
a = 2.1 × 103 M−1) in CH3CN–H2O (3:7, v/v) with detection limit of 1 μM. More fluorescence enhancement was observed when 1 selectively detected Fe3+ or Hg2+ in CH3CN and its detection limit was up to 0.03 μM. 相似文献
13.
T. Maggos J.G. Bartzis P. Leva D. Kotzias 《Applied Physics A: Materials Science & Processing》2007,89(1):81-84
Materials that contain a photocatalyst have a semi-permanent capacity for removing harmful gases from the ambient air. It
is the purpose of this study to investigate the photocatalytic activity of commercial paints containing TiO2 nanoparticles towards NO and NO2. Experiments were carried out in a stainless steel (30 m-3) walk-in type environmental chamber (Indoortron), under “real world setting” conditions of temperature, relative humidity,
irradiation and pollutant concentrations. Two types of nanoparticle TiO2-containing paints were tested for their depolluting properties: a mineral silicate paint and a water-based styrene acrylic
paint. The results showed a significant effect of TiO2-materials in reducing NOx. It was found that up to 74% of NO and 27% of NO2 were photo-catalytically degraded by the mineral silicate paint, while degradation percentage using the styrene acrylic paint
reached 91% and 71% for NO and NO2, respectively. The photo-catalytic rate of NO on the mineral and styrene acrylic paint was calculated to 0.11 μg m-2 s and 0.18 μg m-2 s, respectively, indicating higher photocatalytic performance of the organic based material. The effect of relative humidity
(RH) was also investigated. An increase of RH from 20% to 50% inhibited the NOx photocatalysis on the surface of the samples.
PACS 81.16.Hc; 81.65.Mq; 82.33.Tb; 82.50.Hp; 82.65.+r 相似文献
14.
V. G. Ostroumov F. Heine S. Kück G. Huber V. A. Mikhailov I. A. Shcherbakov 《Applied physics. B, Lasers and optics》1997,64(3):301-305
An intracavity frequency-doubled 10%Nd : LaSc3(BO3)4 (Nd : LSB) laser was investigated in different resonator configurations and in different operation modes under continuous
wave (cw) and quasi-cw laser-diode pumping. With a Cr4+ : YAG passive modulator and a KTP crystal the second-harmonic output power at 531 nm amounted to 190 mW in Q-switched TEM00 mode at 750 mW of pump power. In a sandwich resonator, when all the optical elements were in direct contact with each other,
0.8 W of green output power was obtained in cw mode under 2.7 W of pump power with a slope efficiency of 44%. In the same
setup under fiber-coupled diode-laser array pumping (5.6 W of incident power), 1.2 W of green output power was achieved in
cw mode and 1.4 W in quasi-cw mode.
Received: 30 April 1996/Revised version: 1 July 1996 相似文献
15.
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
16.
I. Baumann R. Brinkmann M. Dinand W. Sohler L. Beckers C. Buchal M. Fleuster H. Holzbrecher H. Paulus K.-H. Müller T. Gog G. Materlik O. Witte H. Stolz W. von der Osten 《Applied Physics A: Materials Science & Processing》1996,64(1):33-44
The erbium incorporation into LiNbO3 by diffusion doping is investigated in detail by means of Secondary Ion Mass Spectrometry, Secondary Neutral Mass Spectrometry,
Rutherford Backscattering, Atomic Force Microscopy, X-ray Standing Wave technique and optical site-selective spectroscopy.
The diffusion of erbium in LiNbO3 can be described by Fick’s laws of diffusion with a concentration-independent diffusion coefficient. The diffusion constants
and activation energies for Z-cut (X-cut) LiNbO3 are 4.8×10-5 cm2/s (12.0×10-5 cm2/s) and 2.28 eV (2.44 eV), respectively. A limited solubility of erbium in LiNbO3 has to be taken into account increasing exponentially with rising temperature. During the first step of diffusion an Er
x
Nb
y
-oxide layer is formed at the surface of the sample acting as diffusion reservoir. Erbium is incorporated into LiNbO3 on vacant Li-sites slightly shifted from the original Li-position along the (-c)-direction. Site-selective spectroscopy found
four distinguishable energetically different erbium centres at this lattice site resulting from locally different symmetries
of the crystal field.
Received: 21 March 1996 / Accepted: 12 August 1996 相似文献
17.
W. Zhao X. Gao W. Chen W. Zhang T. Huang T. Wu H. Cha 《Applied physics. B, Lasers and optics》2007,86(2):353-359
A novel instrument based on an improved off-axis alignment of integrated cavity output spectroscopy (OA-ICOS) in conjunction
with a wavelength modulation (WM) technique, was developed using a DFB diode laser operating in the near infrared at 1.573 μm
(6357.3 cm-1). The laser-based sensor employed a 44 cm optical cavity that provided an effective absorption path length of ∼68 m. A minimum
detectable absorption of approximately 3.6 ppmv Hz-1/2 or 2.3×10-7 Hz-1/2 per optical pass was obtained using second harmonic detection. We demonstrated that by implementation of the WM technique
to OA-ICOS in the near infrared, the detection sensitivity was improved by a factor of 14 compared to that obtained with OA-ICOS.
Measurements of CO2 mixing ratios in ambient air have been performed by using both OA-ICOS and WM-OA-ICOS techniques for performance comparison.
PACS 42.62.Fi; 07.07.Df; 33.20.Ea 相似文献
18.
Hydroxyl tagging velocimetry (HTV) in experimental air flows 总被引:1,自引:0,他引:1
L.A. Ribarov J.A. Wehrmeyer R.W. Pitz R.A. Yetter 《Applied physics. B, Lasers and optics》2002,74(2):175-183
The new nonintrusive instantaneous molecular flow tagging method, hydroxyl tagging velocimetry (HTV), previously demonstrated
only for high-temperature reacting flows, is now demonstrated in low-temperature (300 K) ambient air flowfields. Single-photon
photodissociation of ground-state H2O by a ∼193-nm ArF excimer laser ‘writes’ very long grid lines (>50 mm) of superequilibrium OH and H photoproducts in a room
air flowfield due to the presence of ambient H2O vapor. After displacement, the positions of the OH tag lines are revealed through fluorescence caused by A2Σ+ (ν′=0)?X2Πi (ν′′=0) OH excitation using a pulsed frequency-doubled dye laser with an operating output wavelength of ∼308 nm. The dye ‘read’
laser accesses the strong Q1(1) line, compensating for the relatively weak 193-nm absorption of room-temperature H2O. The weak absorption of ground vibrational state H2O has previously precluded the use of HTV at low temperatures, since previous HTV systems relied on a KrF excimer ‘read’ laser
that could only access a weak (3?0) OH transition. The instantaneous velocity field is determined by time-of-flight analysis.
HTV tag lifetime comparisons between experimental results and theoretical predictions are discussed. Multiple-line tag grids
are shown displaced due to an experimental air flowfield, thus providing 2-D multipoint velocity information. Due to the instantaneous
nature of the HTV tag formation, HTV is particularly suitable for, but not limited to, a variety of fast flowfield applications
including nonreacting base flows for high-speed projectiles and low-temperature hypersonic external or internal flows.
Received: 3 July 2001 / Revised version: 6 November 2001 / Published online: 17 January 2002 相似文献
19.
Nitrous acid (HONO) is important as a significant source of hydroxyl radical (OH) in the troposphere and as a potent indoor
air pollutant. It is thought to be generated in both environments via heterogeneous reactions involving nitrogen dioxide (NO2). In order to enable fast-response HONO detection suitable for eddy-covariance flux measurements and to provide a direct
method that avoids interferences associated with derivatization, we have developed a 2-channel tunable infrared laser differential
absorption spectrometer (TILDAS) capable of simultaneous high-frequency measurements of HONO and NO2. Beams from two mid-infrared continuous-wave mode quantum cascade lasers (cw-QCLs) traverse separate 210 m paths through
a multi-pass astigmatic sampling cell at reduced pressure for the direct detection of HONO (1660 cm−1) and NO2 (1604 cm−1). The resulting one-second detection limits (S/N=3) are 300 and 30 ppt (pmol/mol) for HONO and NO2, respectively. Our HONO quantification is based on revised line-strengths and peak positions for cis-HONO in the 6-micron spectral region that were derived from laboratory measurements. An essential component of ambient HONO
measurements is the inlet system and we demonstrate that heated surfaces and reduced pressure minimize sampling artifacts. 相似文献
20.
F. Gueye E. Safari M. Chenevier G. Guelachvili N. Picqué 《Applied physics. B, Lasers and optics》2005,81(8):1143-1147
A high-resolution time-resolved Fourier transform interferometer is combined with a multimode Cr4+:YAG laser for intracavity laser absorption spectroscopy (ICLAS) experiments. Atmospheric absorption spectra are recorded
in the 1.5 μm region with a minimum detectable absorption coefficient equal to 8×10-11 cm-1 Hz-1/2. The broad gain bandwidth of the crystal allows a simultaneous spectral coverage at most equal to 38 nm. The laser tunability
covers the 1360–1577 nm range. Water vapor detection domain extends from the 100 ppmv down to the 0.1 ppbv level.
PACS 42.62.Fi; 39.30.+w; 07.60.Ly; 33.20.Ea 相似文献