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1.
We have measured the absorption cross sections of oxygen molecules in oxygen and in an oxygen-argon mixture heated by a shock
wave, in the wavelength range 190–250 nm at temperatures of 1500–7000 K, for thermal equilibrium conditions behind the shock
wave front. Analysis of the absorption cross sections obtained allowed us to select a data set that adequately describes the
absorption characteristics of the electronic transition X3Σ
g
−
→ B3Σ
u
−
for the oxygen molecule.
In order to approximate the temperature dependence of these cross sections at a temperature of 1500–4500 K, we chose the function
σ(λ, T) = σ0(λ)(1 − exp (−θ/T)) exp (− n*θ/T) where θ0 = 1.4·10−17, 1.4·10−17, 1.2·10− 17, and 1.3·10−17 cm2, n* = 3.1, 4.1, 5.6, and 7.47 for wavelengths 190, 210, 230, and 250 nm, respectively; θ = 2240 K is the characteristic temperature
of the O2 molecules. The approximation error was 19–25% and did not exceed the experimental error.
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Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 13–17, January–February, 2006. 相似文献
2.
Jon D. Koch Joachim Gronki 《Journal of Quantitative Spectroscopy & Radiative Transfer》2008,109(11):2037-2044
Gas phase acetone and 3-pentanone absorption cross sections have been measured in shock-heated gases in the wavelength range from 220 to 340 nm (the n−π* system) at temperatures between 300 and 1100 K. Absorption measurements using a deuterium source and a kinetic spectrograph enable accurate, broadband measurements of absorption cross sections while simultaneously observing decomposition at elevated temperatures, thus minimizing errors due to product formation. The absorption spectra of both ketones increase in strength and shift to the red with increasing temperature. The spectra are fitted to a parameterized Gaussian curve to allow for calculations of the cross sections as a function of temperature and wavelength. 相似文献
3.
《Proceedings of the Combustion Institute》2023,39(4):4365-4375
The interaction between ammonia (NH3) and nitric oxide (NO) at high temperatures is studied in this work using a shock tube combined with laser absorption diagnostics. The system simultaneously measured the NH3 and NO time-histories during the reaction processes of the shock-heated NH3/NO/CO/Ar mixtures (NH3:NO ≈ 0.9:1.0 and 1.4:1.0). The absorption cross-sections of NH3 near 1122.10 cm–1 and NO at 1900.52 cm–1 (characterized in this study) were used for measuring NH3 and NO time-histories with the temperature measured by two CO absorption lines. The measured NH3 and NO time-histories at 1614–1968 K and 2.4–2.8 atm were compared with predictions of seven recent kinetics models. The predictions that based on different mechanisms are very different and the measured profiles are within the range of the predictions. The Glarborg, NUI Galway Syngas-NOx, and Mathieu mechanisms give the closest predictions to the measurements. Kinetics analyses indicate that the NH3 and NO consumption rates are extremely sensitive to the rate constants and branching ratio of NH2 + NO = N2 + H2O and NH2 + NO = NNH + OH, which are more reliably represented in the Glarborg and NUI Galway Syngas-NOx mechanisms. The performances of Glarborg mechanisms at lower initial temperatures can be apparently improved by revising the rate constants and branching ratio of NH2 + NO = N2 + H2O and NH2 + NO = NNH + OH. These two reactions are also the primary pathways for NO reduction and NH3 is mainly consumed via NH3 + OH = NH2 + H2O and NH3 + H = NH2 + H2. Trace amounts of NO2 and N2O impurities decompose to form O radical followed by the generation of OH radical via H-abstraction reactions, which significantly affects the predictions of NH3 and NO according to kinetics analyses. 相似文献
4.
Simultaneous measurements of CO and CO2 at elevated temperatures are demonstrated using a single semiconductor distributed-feedback (DFB) laser near 1570 nm. Wavelength modulation spectroscopy with second-harmonic detection is used to improve the detection sensitivity and accuracy. A proper line pair near 6368.086 and 6368.330 cm?1 is selected using some line-selection criterions for the target temperature range of 300–1000 K. Normalization of the 2f signal with the 1f signal magnitude is used to remove the need for calibration and correct for transmission variation due to beam steering, mechanical misalignments, soot, and windows fouling. The CO and CO2 concentrations measurements are within 2.21% and 2.55% of the expected values over the tested temperature range of 300–1000 K. The minimum detectable concentrations of CO and CO2 at 1000 K are 80 ppm m and 153 ppm m, respectively. 相似文献
5.
Absorption of CO laser radiation (v = 8→7, J = 14→15 transition at 1901.762 cm-1) by H2O has been studied in shock-heated H2/O2/Ar mixtures over the temperature range 1300–2300 K. This laser transition is nearly coincident with the v2-band 123,10←112,9 transition of H2O at 1901.760 cm-1, thereby providing a convenient and sensitive absorption-based H2O diagnostic useful for studies of combustion. The collision-broadening parameter for this H2O line, due to broadening by Ar, was determined to be 2γ (cm-1atm-1) = 0.027 (T/1300)-0.9 in the temperature range 1300–2300 K. Calculations of the H2O absorption coefficient (at 1901.762 cm-1) based on this expression for 2γ are presented for the temperature range 300–2500 K and pressure range 0.3–1 atm. 相似文献
6.
The modulated phase of (C3H7NH3)CuCl4 stable between 386 and 412 K has been analyzed by single-crystal X-ray diffraction. The structure was solved in the frame of the superspace group approach. The modulation is characterized by a wavelike displacement of the CuCl4 layer. 相似文献
7.
P.S Erdman M Fajardo K.M Sando W.C Stwalley 《Journal of Quantitative Spectroscopy & Radiative Transfer》2004,88(4):447-481
Experimental results are reported for a unique spectroscopic device called the Plasma Spectroscopy Cell. Optical absorption of lithium metal vapor was observed at high density and temperature. Absorption spectra are analyzed using theoretical calculations of absorption cross sections for lithium-helium interactions, and singlet and triplet state transitions of diatomic lithium in the visible spectral range. This is believed to be the most complex example yet calculated in which absolute bound-bound, bound-free, free-bound, and free-free contributions for all possible optically allowed transitions are all included, in quite respectable agreement with experiment. 相似文献
8.
T.S. Luk T. Mclellan G. Subramania J.C. Verley I. El-Kady 《Photonics and Nanostructures》2008,6(1):81-VII
An accurate methodology is presented to measure photonic crystal emissivity using a direct method. This method addresses the issue of how to separate the emissions from the photonic crystal and the substrate. The method requires measuring two quantities: the total emissivity of the photonic crystal–substrate system, and the emissivity of the substrate alone. Our measurements have an uncertainty of 4% and represent the most accurate measure of a photonic crystal's emissivity. The measured results are compared to, and agree very well with, the independent emitter model. 相似文献
9.
M.Y. Louge R.K. Hanson E.C. Rea R.A. Booman 《Journal of Quantitative Spectroscopy & Radiative Transfer》1984,32(4):353-362
A spectral survey of NCO absorption near the P2 + pQ12 head of the [A2Σ + (0000)←X2Πi(0010)] band was obtained at 1450°K, 0.6 atm using a remotely located cw ring dye laser source and a shock tube. Mixtures of hydrogen cyanide, oxygen and nitrous oxide diluted in argon were shock heated to provide a reproducible steady-state concentration of NCO, and narrow-line absorption was measured in repeated experiments with the laser set at different wavelengths. The peak absorption was found at 440.479 nm (vac). The experimental spectrum was compared with a theoretical model to yield an average Voigt parameter a ? 0.1. Additional experiments, in mixtures of cyanogen, oxygen and nitrous oxide diluted in argon, provided a known plateau level of NCO, which was used to infer an absolute absorption coefficient β(1450°K, 0.60 atm) = 110(-50, +130) cm-1 atm-1 at 440.479 nm. This value of β corresponds to an oscillator strength of 0.0026 for the (0000←0010) band.Similar experiments were conducted to monitor the absorption around the R1 head of the [B2Πi(1010)←X2Πi(0010)] band of NCO, using a frequency doubled cw ring dye laser. The observed spectrum displayed strong broadening, indicating predissociation of the upper state. At the peak absorption wavelength (304.681 nm, vac), we inferred β(1470°K, 0.63 atm) = 40(-19, +48) cm-1 atm-1 and a ? 9. This value of β corresponds to an oscillator strength of 0.0031 for the (1010←0010) band. 相似文献
10.
C. Paulmann 《Phase Transitions》2013,86(1-3):77-90
High temperature X-ray diffraction and quenching experiments of mullite single crystals with Al2O3:SiO2 ratio 2:1 have been performed to investigate the stability of the oxygen vacancy ordering close to the melting point of mullite. The experiments show that the structure of mullite exhibits an extremely stable, temperature-independent incommensurate modulation. Inspection of satellite reflections at different temperatures leads to the conclusion that the ordering scheme of oxygen vacancies after the crystallization of mullite persists to the melting point and does not show any disordering effects. The experimental results are in agreement with former theoretical calculations using a statistical mechanics approach which yield the critical temperature Tc > 3000°C. 相似文献
11.
A program for calculating the absorption and emission spectra of diatomic molecules that can take into account the vibrational-rotational interaction and nonequilibrium conditions of the gaseous medium is created. The program also allows one to perform calculations for a particular experimental setup by specifying the corresponding instrumental function. The absorption cross sections of molecular oxygen are calculated in the Schumann-Runge system for the temperature range 1000–6000 K and the wavelength interval 130–280 nm. These calculations are compared with the experimental data obtained behind the shock wave front in oxygen-argon mixture at different temperatures for a number of wavelengths in the range of 160–270 nm. 相似文献
12.
应用自恰变分自由能模型描述了在化学平衡下,H2,H,H ,e构成地混合物在天体物理和高压实验中遇到情形下的各种相互作用及压力与温度效应引起地离解和电离现象.目前的模型预测了在压力电离区存在一热力学不稳定状态,当温度Tc=15.5 kK,压力Pc=58.3 GPa和密度ρc=0.3226 g/cm3时发生等离子体相变,此理论预测结果与各种模型计算结果进行了比较分析. 相似文献
13.
14.
可调谐半导体激光吸收光谱法对高温甲烷的测量研究 总被引:1,自引:0,他引:1
可调谐半导体激光吸收光谱(TDLAS)是一种具有高灵敏度、高分辨率、快速检测特点的气体检测技术,已广泛用于大气中多种痕量气体的检测以及地面的痕量气体和气体泄漏的检测。研究了利用TDLAS技术测量高温下甲烷浓度的实验方法,使用可加热的静态吸收池对在1653.72nm波长附近R(3)支转动跃迁的吸收线进行了测量,并计算了吸收线强。分别在相同温度不同浓度和相同浓度不同温度的两种条件下进行了实验。结果表明,利用直接吸收的方法,在实验室可以得到370K时的最小可探测限为100×10-6,500K时的最小可探测限为245×10-6(吸收池长度为10cm),可以应用在燃烧控制及喷焰气体浓度测量等多个领域。 相似文献
15.
A derivation is given for the integrated absorption coefficient of pressure-induced pure rotational and vibrational transitions in binary collisions of homonuclear diatomic molecules of the same chemical species. The previously neglected effects of excited vibrational states, mechanical anharmonicity, and vibration-rotation interaction are taken into account to obtain more accurate absorption coefficients at high temperatures. In the region of the fundamental wave number the excited vibrational states make more of a contribution to the absorption than their relative population would lead one to expect. 相似文献
16.
In this research the Hall mobility of electrons in single crystal and Li-doped polycrystalline MnO was measured. It was found that μnH is equal to 10 cm2 /V-sec in the range of temperatures 943–1210°C. 相似文献
17.
Laboratory measurements of the absorption cross-section of the Schumann-Runge continuum of O2 at the temperatures 90 and 295 K have been made in the wavelength region 130-175 nm. The absolute absorption cross-sections at the same temperatures have been measured at several discrete wavelengths through the region. The absolute cross-sections of the O2 continuum have been used to put relative cross-sections on a firm absolute basis throughout the region 130-175 nm. These recalibrated cross-sections are available as numerical compilations. 相似文献
18.
We show that when polystyrene is exposed (for 15–60 sec) to a UV laser light beam (λ = 248 nm), its absorption and luminescent
properties change significantly. In the irradiated polymer, optical centers are formed with absorption bands in the 280–460
nm region and fluorescence bands in the 330–520 nm region. We have established the chemical structure of the optical centers
for fluorescence of polystyrene.
__________
Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 1, pp. 54–58, January–February, 2006. 相似文献
19.
In this paper, stable single-mode operation at high temperatures is produced by the surface-relief-integrated vertical cavity surface emitting laser(VCSEL). The gain-cavity mode detuning technique is employed to realize high operating temperatures for the VCSEL. The surface relief is etched in the centre of the top side as a mode discriminator for the fundamental mode output, and the threshold current minimum is 1.94 mA at high temperatures by the gain-cavity mode detuning technique. Maximum single-fundamental-mode output power of 0.45 mW at 80℃ is obtained, and the side mode suppression ratios(SMSRs) are more than 30 dB with increasing temperature and current, respectively. 相似文献
20.
L. Torrisi S. Gammino A. M. Mezzasalma C. Gentile J. Krsa L. Lska K. Rohlena J. Badziak P. Parys J. Wolowski 《Applied Surface Science》2003,220(1-4):193-202
The high power pulsed laser Prague asterix laser system (PALS), operating at the fundamental (1ω) and third (3ω) harmonics (1315 and 438 nm wavelengths, respectively), is employed in a single-shot mode to irradiate tantalum targets in vacuum. The laser pulse width is 400 ps and the laser pulse energy ranges between 43 and 736 J at 1ω and between 12 and 230 J at 3ω. High ablation yields (0.1–0.6 mg per pulse) are measured as a function of the laser pulse energy at both wavelengths; at 438 nm higher etching rates are observed. The produced craters are analysed by the scanning electron microscope (SEM) and by the high sensitivity surface profiler system. They are investigated in dimension, shape and angle aperture as a function of the incident laser energy. Different possible mechanisms responsible for the different crater shapes are presented and discussed. 相似文献