共查询到20条相似文献,搜索用时 15 毫秒
1.
A. O. Vyrodov J. Heinze M. Dillmann U. E. Meier W. Stricker 《Applied physics. B, Lasers and optics》1995,61(5):409-414
Laser-Induced Fluorescence (LIF) excitation spectra in the NOA–X (0-0) band were used for temperature measurements in the postflame region of high-pressure CH4/air flames. To improve the quality of the measured spectra and to perform reliable line-shape measurements, the initial mixture was doped with approximately 400 ppm NO. At pressures up to 18 bar, excellent agreement was obtained between NO LIF temperatures and NARS/rotational Raman temperatures. Effective broadening coefficients were also determined in these flames. Problems with quantitative concentration measurements of NO and single-pulse temperature measurements at high pressures are discussed. 相似文献
2.
Laser-induced fluorescence is used to detect and record profiles of acetylene formed as an intermediate species in 10-Torr
premixed propane and methane flames. In low-temperature regions of the flames, excitation spectra confirm acetylene as the
spectral carrier. The spectra of acetylene overlap those of O2 and NO in terms of both excitation and detection wavelengths, however, acetylene can be detected with relatively little interference
in the vicinity of 228 nm, using a detection wavelength of 260 nm. The fluorescence lifetime of acetylene in the flame conditions
studied is approximately 20 ns, much shorter than the radiative lifetime, due to a high quenching rate for all the colliders
investigated. This can be exploited in low-pressure flames to avoid interference from acetylene in monitoring nitric oxide.
The acetylene mole fraction in propane flames reaches its peak value at nearly the same location as that of HCO, slightly
closer to the burner than the peak CH mole fraction. The acetylene fluorescence signal is easily detected in propane flames
over equivalence ratios from 0.6 to 1.2, although it increases under fuel-rich conditions. In methane flames, the acetylene
signal is much weaker and is undetectable for fuel-lean conditions.
Received: 5 August 2002 / Revised version: 30 September 2002 / Published online: 20 December 2002
RID="*"
ID="*"Corresponding author. Fax: +1-202/767-1716, E-mail: brad@code6185.nrl.navy.mil 相似文献
3.
An experimental arrangement is described which allows the detection of low gas densities by resonance fluorescence in the
vacuum ultraviolet. As a light source a capillary discharge through helium was used. Fluorescence signals as a function of
density have been measured in krypton, deuterium, and hydrogen, and the results have been compared with calculations. Detection
limits of 3·109 atoms/cm3 have been obtained. 相似文献
4.
T. M. Quagliaroli G. Laufer J. C. McDaniel 《Applied physics. B, Lasers and optics》1994,59(6):635-638
A method for the calibration of OH temperature measurements using laser-induced fluorescence is demonstrated. The technique depends on the thermal dissociation of water vapor in a furnace. The calibration was demonstrated for the excitation of theA
2
+( = 3) –
2
( = 0) band with a tunable KrF laser. Consistent discrepancies of 3% between calculated and measured temperatures with a standard deviation of 8 % were observed. 相似文献
5.
By use of Laser-Induced Fluorescence (LIF) the absolute concentration of the C2 radical in a microwave excited diamond chemical vapour deposition plasma has been measured for the first time. LIF spectra of thed
3
g–a
3
u (1,0) Swan band near 473 nm were recorded and synthesized theoretically allowing the plasma temperature of 2100 ± 200 K to be inferred. Quenching rates were determined from time-resolved measurements of the fluorescence decay. By calibrating the LIF detection system, using spontaneous Raman scattering in H2 in the reactor vessel, the absolute concentration of C2 was determined to be (7.5 ± 1.7) × 1010 cm–3. Observations of the C2 density under varying plasma conditions are reported. 相似文献
6.
Four wavelength extensions have been investigated by stimulated Raman scattering in hydrogen or deuterium gas of the 248 nm fundamental output of a narrow-band tunable KrF excimer laser. They have been used to acquire laser-induced fluorescence spectra of NO and OH in flames at atmospheric pressure. NO is detected in relatively high rotational states within the -band electronic system at 225 nm. OH was excited at 291.5 nm in the (1–0), at 313 nm in the (1–1) and at 268.5 nm in the predissociative (3–1) band of the 2–2 electronic band system, respectively. Prospects of 2D imaging for concentration and temperature measurements in flames using these wavelength extensions are discussed. 相似文献
7.
P. Karlitschek F. Lewitzka U. Bünting M. Niederkrüger G. Marowsky 《Applied physics. B, Lasers and optics》1998,67(4):497-504
Fluorescence spectra, decay times, and detection limits of the 16 US-EPA polycyclic aromatic hydrocarbons (PAH) have been
measured and the results are discussed in terms of separability of single PAHs in a multicomponent mixture. The results of
a mathematical analysis of a 16-component mixture is presented. Spectra from natural water samples contaminated with gasoline
and tar are also presented and the potential and limits of the LIF technique are discussed.
Received: 19 March 1998/Revised version: 2 June 1998 相似文献
8.
Pb2, which occurs in lead vapor, was studied by the technique of laser-induced fluorescence using single-mode Ar-laser excitation. The fluorescence observed could be classified into the F-X system. Ten progressions involving vibrational quantum numbers v′ = 0?9 and v″ = 0?22 were analyzed. Including collision-induced lines, rotational quantum numbers from J = 25 to J = 300 were observed. The vibrational constants and the numbering of the states had to be reassigned. For the first time rotational constants were determined for the Pb2 molecule. The internuclear distances of 208Pb2 in the F and X state are and , respectively. Using the constants derived RKR potentials and Franck-Condon factors were calculated, which confirmed the vibrational assignments and constants. 相似文献
9.
Donor (anthracene) sensitized acceptor (perylene) fluorescence is quenched more efficiently by halothane than is intrinsic perylene fluorescence. The underlying process of dynamic fluorescence quenching is investigated by time-resolved fluorescence spectroscopy. 相似文献
10.
Yu. P. Meshalkin O. P. Cherkasova V. I. Fedorov E. S. Samoilova 《Optics and Spectroscopy》2002,92(1):32-35
Spectra of the laser-induced fluorescence of estrogens—estradiol, estriol, and estrone—were measured under excitation by the fourth harmonic (λ=266 nm) of a Nd:YAG laser. Quantum yields of the fluorescence were evaluated by the relative technique to be 0.107 for estradiol, 0.116 for estriol, and 0.0052 for estrone. The water solution of tryptophan is used as the standard. 相似文献
11.
《Journal of Molecular Spectroscopy》1987,124(2):243-271
A semiempirical calculation of the energy level diagram of GdO based on the ligand field theory is presented here. The main frame of the resulting scheme is very simple and should be useful in order to link together the numerous observed systems of GdO. Pulsed dye laser-induced fluorescence experiments made possible the evaluation of some of the ligand field theory predictions, particularly that a Y7Σ− level is lying 1840 cm−1 above the X9Σ− ground state. The I and II systems are shown to arise from the B9Σ−-X9Σ− and B17Σ−-Y7Σ− transitions, respectively. Continous wave laser-excitation spectra have been recorded and rotational analysis of the A9Π4 → X9Σ− transition carried out, confirming previous results of N. N. Dmitriev, L. A. Kaledin, E. A. Shenyavkaya, and L. V. Gurvich (Acta Phys. Hung. 55, 467–479 (1984)). 相似文献
12.
R. S. Karve S. K. Sarkar K. V. S. Rama Rao J. P. Mittal 《Applied physics. B, Lasers and optics》1991,53(2):108-114
The dissociation of UF6 sensitized by multiple photon excitation of a series of halomethanes: CF4, CF3Cl, and CF2Cl2 has been investigated. The roles of various experimental parameters like exciting frequency, fluence and pressures of sensitizer/UF6 on the dissociation yield were studied to examine (1) the characteristics of the sensitizer/UF6 system and (2) the coupling of vibrational energy between two molecular systems. The efficiency of the energy transfer process was estimated on the basis of long range dipole-dipole interaction to gain an understanding of the dissociation process. 相似文献
13.
Received: 11 January 1996/Revised version: 25 July 1996 相似文献
14.
15.
16.
Dominic Lingenfelser 《Applied Surface Science》2007,253(19):7749-7754
Functionalization of materials and laser patterning of chemisorbed layers play an increasing role in tailoring and structuring surface properties on the nanoscale. An attractive method of investigating organic functionalizations is laser-induced thermal desorption (LITD). The analysis of well-defined H- and D-terminated Si(1 1 1)-(1 × 1):H(D) surfaces was used to quantify the LITD technique. Moreover, oxidized silicon surfaces were functionalized with trimethylsilyl (TMS) and (3,3,3-trifluoropropyl)-dimethylsilyl (TFP) hydrophobic end groups. The samples were irradiated normal to the surface with focused XeCl laser pulses. The desorbed species were monitored at an oblique angle and their time-of-flight (TOF) distributions were measured with a quadrupole mass analyzer. The TOF temperatures of silicon were calibrated for different laser pulse energies by desorption of H2 and D2. In the LITD experiments, the desorption of trimethylsilanol groups was observed for TMS terminations, indicating that essentially the whole molecule desorbs from the surface. The TOF data could be fitted to Maxwellian distributions, providing the desorption yield of the emitted species, their mass, and temperature. On the other hand, several characteristic fragments were found for the TFP-terminated surface. The TOF distributions indicate that the fragments detected with the analyzer derived from different desorbed species. 相似文献
17.
T. Okada M. Maeda Y. Kajiki K. Muraoka M. Akazaki 《Applied physics. B, Lasers and optics》1987,43(2):113-116
The sensitive detection of H2 molecules was demonstrated by means of twophoton excited laser-induces fluorescence spectroscopy with a narrow-band ArF excimer laser. A detection limit of 2×1014 cm–3 was obtained with an excitation power of 150 kW. This is already comparable with that obtained by the coherent anti-Stokes Raman scattering (CARS). This technique was successfully applied to measure a spatial distribution of H2 in a town-gas burner. 相似文献
18.
Pulsed laser induced oxidation of clean Si(111) surfaces has been studied by Auger electron spectroscopy and electron energy loss spectroscopy. The short duration time of the pulse has allowed a precise investigation of the first stages of the oxidation. About 1–2 oxide monolayers first grow in less than 10 s. Their stoichiometry evolves from SiOx towards SiO2 with increasing beam energy densities. Once this superficial layer has formed, no evolution is seen with further irradiation, suggesting that oxygen diffusion during the pulse duration cannot sustain the oxide growth. 相似文献
19.
Using a pulsed capilary discharge through helium as a light source fluorescence within the Lyman bands (transitionX
1 ∑
g
+
→B
1 ∑
u
+
of molecular hydrogen and deuterium has been investigated. Selecting a narrow spectral range (width ≈ 8 ?) from the continuum
radiation with a spectrometer, lines in the wavelength range from 1060 ? to 1110 ? have been excited having a vibrational
quantum number υ″=0 in the lower state, and ≦υ′≦4 in the upper state. The fluorescence intensity has been measured as a function
of υ′ and of the hydrogen density. Agreement with calculations has been found to be within ±30%. The method at present allows
the determination of densities between 1010 and 1015 molecules per cm3 with a temporal resolution of 1μs and with a spacial resolution of 0.1 cm3 相似文献
20.
The fluorescence lifetime of photo-oxidative emission at 360 nm becomes shorter when stabilizer is added to polyethylene film. A broad emission band at 450 nm is attributed to the emission from a charge transfer complex. The preliminary results show that the quenching of photo-oxidative emission and the fluorescence intensity decay can be used to evaluate the extent of photo-stability of polyethylene films. 相似文献