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1.
Simultaneous imaging of laser-induced fluorescence of toluene and 3-pentanone was used to determine the local absolute oxygen
and residual gas concentrations present within an engine. The technique utilizes the different sensitivities of the laser-excited
molecules to quenching by molecular oxygen as a means to determine quantitative images of in-cylinder oxygen concentrations.
The difference in the amount of oxygen available between two operating conditions was investigated. Results are in agreement
with measurements in the exhaust gas.
Received: 4 June 2002 / Published online: 8 August 2002 相似文献
2.
We report spatially resolved linear laser-induced fluorescence (LIF) and planar laser-induced fluorescence (PLIF) measurements
of nitric oxide (NO) in a pre-heated, high-pressure (4.27 atm), lean direct-injection (LDI) spray flame. The feasibility of
using PLIF in lieu of LIF is assessed with respect to measuring NO concentrations in high-pressure LDI spray flames. NO is
excited via the resonant Q2(26.5) transition of the γ(0,0) band while a non-resonant wavelength is employed to subtract background interferences. LIF
detection is performed in a 2-nm region centered on the γ(0,1) band. PLIF detection is performed in a 68-nm window that captures
fluorescence from several vibrational bands. An in situ NO doping scheme for fluorescence calibration is successfully employed
to quantify the LIF signals. However, a similar calibration scheme for the reduction of PLIF images to quantitative field
measurements is plagued by the laser-excited background. Excitation scans and calibration comparisons have been performed
to assess the background contribution for PLIF detection. Quantitative radial NO profiles measured by LIF are presented and
analyzed so as to correct the PLIF measurements to within the accuracy bars of the LIF measurements via a single-point scaling
of the PLIF image.
Received: 23 November 1999 / Revised version: 17 January 2000 / Published online: 27 April 2000 相似文献
3.
S. Böckle J. Kazenwadel T. Kunzelmann D.-I. Shin C. Schulz 《Applied physics. B, Lasers and optics》2000,70(5):733-735
Single-shot formaldehyde laser-induced fluorescence (LIF) imaging measurements in a technical scale turbulent flame have been
obtained using XeF excimer laser excitation in the ?1A2-˜X1A1 transition at 353.2 nm. Measurements have been carried out in a 150 kW natural gas swirl burner where formaldehyde distribution
fields have the potential, in combination with OH concentration fields, to visualize the heat release distribution and therefore
give an optimal visualization of flame-front positions. The extended areas where formaldehyde was detected in the swirl flame
indicates the presence of low temperature chemistry in preheated gas pockets before ignition.
Received: 31 January 2000 / Revised version: 2 March 2000 / Published online: 5 April 2000 相似文献
4.
We report a new imaging diagnostic suitable for measurements of infrared-active molecules, namely infrared planar laser-induced
fluorescence (IR PLIF), in which a tunable infrared source is used to excite vibrational transitions in molecules and vibrational
fluorescence is collected by an infrared camera. A nanosecond-pulse Nd:YAG-pumped KTP/KTA OPO/OPA system is used to generate
12 mJ of tunable output near 2.35 μm which excites the 2ν band of carbon monoxide (CO); fluorescence resulting from excited
CO is collected at 4.7 μm by using an InSb focal plane array. Quantitative, high-SNR PLIF imaging of gas-phase CO is demonstrated
at a 10-Hz acquisition rate with a minimum detection limit of 1350 ppm at 300 K.
Received: 30 July 1999 / Published online: 16 September 1999 相似文献
5.
Experimentally-based correction procedures are demonstrated which enhance the quantitative nature of planar laser-induced
fluorescence (PLIF) images for mean species concentration by correcting for the influence of the electronic quenching rate
coefficient. Implementation of these methods requires only the ability to make PLIF and laser-saturated fluorescence (LSF)
measurements. Though applied herein to NO, these procedures are broadly applicable both in terms of species and users. Moreover,
they are generally effective regardless of the error gradients associated with spatial variations in the electronic quenching
rate coefficient. In such general environments, these methods produce quenching-corrected, spatially resolved PLIF images
of mean species concentration with a total uncertainty equivalent to that of a single LSF measurement.
Received: 22 November 1999 / Revised version: 3 March 2000 / Published online: 16 June 2000 相似文献
6.
David J. Creasey Dwayne E. Heard Michael J. Pilling Benjamin J. Whitaker Martin Berzins Roger Fairlie 《Applied physics. B, Lasers and optics》1997,65(3):375-391
2 Σ+, v′=0) by air at 26±4 K. A value of 2.56±0.40×10-10 molecule-1 cm3 s-1 was obtained, a factor of more than four higher than at room temperature, and consistent with attractive forces dominating
the quenching of OH(A2Σ+). A d
etailed computational fluid dynamics (CFD) simulation of the supersonic free-jet expansion was performed, providing a two-dimensional
visualisation of temperature and density variations throughout the expansion. The CFD calculations reproduced the salient
features of the experimental temperature and density profiles along the centreline. Comparison between experiment and computation
has allowed validation of CFD codes.
Received: 31 January 1997/Revised version: 24 March 1997 相似文献
7.
We point out the influence of the different noise sources which occur in the detection of the fluorescence signal induced by a laser in an atomic beam. We have developed a theoretical model which takes account of the atomic shot noise, photon noise, laser-frequency noise and a partition noise linked to the imperfect detection of the fluorescence photons. The calculations have been performed for two- and three-level atomic systems. We detail the own contribution of each noise source and give some predictions concerning the value of the fluorescence signal to noise ratio. We determine predominance domains of each noise source which depend on the values of key parameters such as the atomic flux intensity and the laser spectral linewidth. We particularly show that the laser-frequency noise, which induces a coupling between the emission of fluorescence photons by various atoms, leads to a saturation of the S/N ratio for intense atomic fluxes. Moreover, we point out that the optical pumping process associated with a three level atomic system leads to an interesting laser-noise filtering effect. 相似文献
8.
D.N. Kozlov B. Hemmerling A. Stampanoni-Panariello 《Applied physics. B, Lasers and optics》2000,71(4):585-591
We used time-resolved light scattering of cw probe laser radiation from laser-induced electrostrictive gratings for the determination
of flow velocities in air at room temperature. Some possibilities of the technique have been experimentally demonstrated with
submerged planar air jets in atmosphere, both for accumulated and single-shot measurements. The range of investigated flow
velocities was 5–200 m/s. The method of data treatment and of the estimate of the experimental parameters is described.
Received: 8 Febuary 2000 / Revised version: 2 May 2000 / Published online: 2 August 2000 相似文献
9.
J. Luque R.J.H. Klein-Douwel J.B. Jeffries G.P. Smith D.R. Crosley 《Applied physics. B, Lasers and optics》2002,75(6-7):779-790
Absolute number densities of the CH radical were determined in a partially premixed methane/air flame (equivalence ratio was
1.36) at atmospheric pressure by exciting a predissociating level via the CH B–X(1,0) transition using a quasi-linear laser-induced
fluorescence scheme. The peak number density was (1.0±0.4)×1013 cm-3 or 2.4±1 ppm at 1900 K, with a flame-front width of 250 μm (FWHM). Rotational energy transfer must be considered for correct
laser-induced fluorescence signal interpretation. Competition between optical pumping and rotational relaxation in both excited
and ground states produces a signal that varies almost linearly with laser pulse energy even for large pumping rates. For
these conditions, the population of the initial ground-state rotational level is depleted by optical pumping, and rotational
energy transfer collisions rapidly repopulate the level during the laser pulse. Deviations from linear behavior are less than
20%. The effects of spatial resolution and polarization of the fluorescence on the absolute measurements are also discussed.
Received: 27 March 2002 / Revised version: 22 August 2002 / Published online: 15 November 2002
RID="*"
ID="*"Present address: Lam Research Corporation, Fremont, CA 94538, USA
RID="**"
ID="**"Present address: Mechanical Engineering, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
RID="***"
ID="***"Present address: Mechanical Engineering Dept., Stanford University, Stanford CA 94305, USA
RID="****"
ID="****"Corresponding author. Fax: +1-650/859-6196, E-mail: smith@mplvax.sri.com 相似文献
10.
The temporal influence of a laser pulse on saturated laser-induced fluorescence is investigated by means of numerical solutions
of rate equations describing dynamical models of two- and four-level molecular systems. It turns out that temporal wings of
the laser become negligible if the saturated fluorescence power from the entire pulse is monitored instead of the total energy
obtained from the integrated fluorescence. The negligibility is evaluated relative to the saturation status obtained with
temporal sampling of the fluorescence signal as is commonly adopted in the time-resolved technique. The advantages and the
limitations of power measurements are discussed with reference to the experimental feasibility of pulse acquisitions for the
determination of the flawless saturation degree.
Received: 4 December 2002 / Revised version: 14 February 2003 / Published online: 5 May 2003
RID="*"
ID="*"Corresponding author. Fax: +39-06/3048-4811, E-mail: michele.marrocco@casaccia.enea.it 相似文献
11.
A. Stampanoni-Panariello D. N. Kozlov P. P Radi B. Hemmerling 《Applied physics. B, Lasers and optics》2005,81(1):101-111
Electrostriction and collisional thermalization of absorbed laser energy are the two dominant mechanisms leading to the formation of laser-induced gratings (LIGs) in the gas phase. In this article the results of the theoretical investigations that have been achieved in the past ten years at the Paul Scherrer Institute on this issue are summarized and yield a comprehensive understanding of the underlying physical concepts. Furthermore, a study of the influence of various parameters, such as the alignment and the spatial intensity profile of the beams on the generated electrostrictive and thermal signal is presented for the first time to the authors’ knowledge. The variations of the refractive index responsible for the appearance of laser-induced gratings have been theoretically described by solving the linearized hydrodynamic equations. The contributions from electrostriction, as well as from instantaneous and slow relaxation of the absorbed radiation energy into heat is obtained. These expressions are employed for analysis of experimental data presented in the companion paper [1] which is devoted to the application of the technique for diagnostic purposes in the gas phase. Much effort has been undertaken in order to allow a straightforward physical interpretation of the experimental findings of the expressions presented here. 相似文献
12.
S.G. Nakhate Sheo Mukund S. Bhattacharyya 《Journal of Quantitative Spectroscopy & Radiative Transfer》2010,111(3):394-225
Radiative lifetimes of 20 odd-parity excited energy levels in Zr I, out of which 10 for the first time, have been investigated in the energy range 17 400-29 300 cm−1. The levels belong to the 4d25s5p and 4d35p electronic configurations. Time-resolved laser-induced fluorescence spectroscopy technique in supersonic free-jet has been employed in the present work to circumvent the effects of collision in lifetime measurements. 相似文献
13.
V. Sick 《Applied physics. B, Lasers and optics》2002,74(4-5):461-463
The potential use of planar laser-induced fluorescence (PLIF) of sulfur dioxide (SO2) for visualization of exhaust-gas distributions is outlined and demonstrated. Strong absorption features in the UV spectral
range allow excitation of SO2 with the fourth harmonic of a Nd:YAG laser at 266 nm. Fluorescence emissions are mostly red-shifted and can be easily detected
in single-shot imaging arrangements with a good signal-to-noise ratio. This study uses a premixed methane/air flame that is
doped with SO2 to demonstrate the technique. The signal strength has a pronounced temperature dependence for excitation at 266 nm.
Received: 14 January 2002 / Revised version: 30 January 2002 / Published online: 14 March 2002 相似文献
14.
Toluene laser-induced fluorescence (LIF) emission spectra were acquired in an optical engine with excitation at 248 nm. Toluene
was homogeneously seeded in pure nitrogen and air which were used as intake gases. Data were acquired during the compression
phase without ignition leading to simultaneous increases in temperature and pressure from 20°C and 1 bar to 500°C and 23.6 bar.
Compared to LIF emission spectra at high temperature and atmospheric pressure reported in the literature, the toluene-LIF
emission signal shifts to longer wavelengths when temperature and pressure increase simultaneously, whereas the spectrally
integrated emission intensity is slightly affected by the pressure level. 相似文献
15.
J. Boneberg H.-J. Münzer M. Tresp M. Ochmann P. Leiderer 《Applied Physics A: Materials Science & Processing》1998,67(4):381-384
Received: 20 April 1998/Accepted: 2 June 1998 相似文献
16.
By focussing a commercial dye laser pumped with a XeCl excimer laser into phase matched Xe-A or Kr-A gas mixtures, radiation at the third-harmonic frequency has been generated in the wavelength regions: 1142–1165, 1178–1186, 1203–1224, and 1268–1290 Å. VUV powers up to about 200 W have been detected by a calibrated Au-photodiode. The vacuum uv radiation has been used for the fluorescence excitation of H and C atoms produced by thermal dissociation or by a gas discharge. Absolute densities have been derived by a comparison of fluorescence intensities with intensities from Rayleigh scattering in argon. As a further application, velocity distributions of C atoms sputtered from a graphite target by 1.5 keV argon ions have been measured. These data are in good agreement with a Thompson distribution corresponding to a surface energy of 8.2 eV. 相似文献
17.
Daobin Luo 《Optik》2014
The theoretical study of fluorescence rate of a single molecule close to a spherical metallic nanoparticle is presented. The dielectric function of the metallic nanoparticle and its polarizability is analyzed when the radii of the nanoparticle is rather small. Based on dipole–dipole model, the distance dependence of the excitation rate, radiation rate, nonradiation rate and quantum yield of the emitter molecule are derived out. The results show that the quantum yield is rather small at the vicinity of the metallic nanoparticle surface. 相似文献
18.
A new regime of chemical oxygen-iodine laser (COIL), high-pressure subsonic mode operation, was demonstrated using a jet-type
singlet oxygen generator (SOG). The laser output power of 342 W with chemical efficiency of 20.9% was obtained at the Cl2 flow rate of 18 mmol/s and the operating pressure of 6.4 Torr in the laser cavity. The specific energy was 3.1 J/l which
was four times higher than our supersonic device, and was comparable to the highest value for the supersonic regime. The experimental
results were in good agreement with the numerical simulation results.
Received: 26 February 1999 / Revised version: 13 July 1999 / Published online: 30 November 1999 相似文献
19.
D. Guo K. Cai Y. Huang L.-T. Li 《Applied Physics A: Materials Science & Processing》2003,76(7):1121-1124
This work reports a novel anti-spatter and anti-crack ceramic laser drilling method based on the gelcasting technique. A Nd:YAG
solid state laser was used to drill micro-holes directly on a gelcast green alumina body. The results reveal that the irregular
spatter at the periphery of the hole inherent to traditional laser drilling methods can be effectively prevented by direct
drilling of the gelcast green body. Much more regular hole shapes without microcracks were also successfully obtained.
Received: 02 October 2002 / Accepted: 07 October 2002 / Published online: 22 January 2003
RID="*"
ID="*"Corresponding author. Fax: +86-10-62771160, E-mail: caikai99@mails.tsinghua.edu.cn 相似文献
20.
G. Dilecce P.F. Ambrico M. Šimek S. De Benedictis 《Applied physics. B, Lasers and optics》2002,75(1):131-135
In this communication, we propose a new laser-induced fluorescence (LIF) scheme that allows the simultaneous detection of
OH and NO by a single laser set-up. OH is detected by the second harmonic (SH) of a dye laser tuned to the (0,0)-band of the
3064 ? system, while its third harmonic (TH) is used to detect NO through excitation of the (2,0)-band of the γ system. This
scheme is presented and discussed within the framework of its potential use in field instruments for the measurement of tropospheric
OH concentration.
Received: 8 March 2002 / Revised version: 22 April 2002 / Published online: 8 August 2002 相似文献