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51.
A technique is described for simultaneous single-shot imaging of OH and O2. Laser-induced fluorescence of both molecules is excited by a tunable KrF laser, which is operated simultaneously on two wavelengths. By using two CCD detectors with image intensifiers and suitable filters, separate images of OH and O2 distributions in H2/O2 and hydrocarbon/air flames were obtained. 相似文献
52.
D.W. Zhang Z.-J. Liu Y.-Z. Wan J.-T. Wang 《Applied Physics A: Materials Science & Processing》1998,66(1):49-51
2 /C2H2 ratio for diamond synthesis in oxyacetylene flames can be theoretically predicted. When the substrate temperature is between
1000 K and 1250 K, the corresponding O2/C2H2 ratio range is about between 0.8 and 1.1. The suitable range of substrate temperature is widest for O2/C2H2 ratio close to unity and is narrowed rapidly when the flow ratio deviates from unity.
Received: 2 March 1997/Accepted: 17 July 1997 相似文献
53.
54.
Andrew D. Sappey David R. Crosley Richard A. Copeland 《Applied physics. B, Lasers and optics》1990,50(6):463-472
Methylene, CH2, is a chemically important intermediate in hydrocarbon combustion but has previously eluded optical detection in a combustion environment. The CH2 signal as a function of height above the burner surface in a premixed, laminar, methane/oxygen flame (5.6 Torr and fuel equivalence ratio 1.05) is measured by laser-induced fluorescence (LIF) in the
B
1 – ã1
A
1 electronic system. The ã state which lies 3165 cm–1 above the ground state is populated at the high temperatures of the flame (800–1800 K). Although less than one photon for each laser pulse is detected, we can unambiguously attribute the LIF features in the region 450 to 650 nm to CH2 by both scanning the excitation laser and dispersing fluorescence. LIF temperatures and CH and OH LIF concentration profiles are also obtained for the flame. The CH2 radical concentration maximum occurs closer to the burner than that of either OH or CH, as expected from models of methane combustion chemistry. 相似文献
55.
R. W. Pitz T. S. Cheng J. A. Wehrmeyer C. F. Hess 《Applied physics. B, Lasers and optics》1993,56(2):94-100
Two-photon laser-induced predissociative fluorescence (LIPF) of H2O is examined as a potential measurement technique of H2O concentration and temperature in flames. Two-photons of 248 nm light from a narrowband KrF laser excite H2O to the highly predissociative
state in a hydrogen-air flame. The subsequent bound-free emission
is observed from 400–500 nm in the flame at temperatures of 1000–2000 K and is found to be free of fluorescence interference from other flame species. This LIPF signal is not affected by collisional quenching due to the short lifetime of the
predissociative state (2.5 ps). Broadband laser dispersion spectra, narrowband laser dispersion spectra, laser excitation spectra and probability density functions of the H2O fluorescence are obtained in the hydrogen flame. The H2O LIPF signal is found to be temperature sensitive and a two-line LIPF technique is needed for concentration and temperature measurement. The accuracy of a two-line LIPF technique for H2O concentration and temperature measurement is determined. 相似文献
56.
J. Hussong R. Lückerath W. Stricker X. Bruet P. Joubert J. Bonamy D. Robert 《Applied physics. B, Lasers and optics》2001,73(2):165-172
This work describes a further step towards the determination of the temperature accuracy of H2 Q-branch CARS (Coherent Anti-Stokes Raman Scattering) at high pressure with regard to the influence of the H2 line widths. In laminar steady H2/air flames in the pressure range 1–15 bar and at fuel-rich conditions with stoichiometries between two and four, quasi-simultaneous
temperature measurements were performed with H2 and N2 CARS. The temperature values deduced from H2 CARS are in good agreement with the reference temperature from N2 CARS. The influence of different line-width contributions on the accuracy of H2 Q-branch thermometry was investigated in detail.
Received: 10 April 2001 / Revised version: 22 May 2001 / Published online: 18 July 2001 相似文献
57.
Many materials are good candidates for diode-pumped ultra-short-pulse lasers: several transition-metal-ion-doped crystals
can or could support extremely short fs pulses. This goal, so far, has only been reached by Cr3+:LiSAF, but there are good chances for other crystals like Cr4+:YAG having its bandwidth within the third communication window, and the high-yield Cr2+:ZnSe with its impressive bandwidth in the near IR. Rare-earth-ion-doped media deliver only sub-ps pulses but allow unprecedented
and scalable high average powers, like a SESAM mode-locked Yb:YAG thin-disk laser described recently. In all ranges of pulse
durations there are fascinating applications ready for widespread employment as soon as compact, reliable and moderately priced
ultra-short-pulse systems will be available for the non-laser-skilled user. The highest impact in the near future is attributed
to microstructuring of materials and processing of biological samples, including dental enamel, by ps and sub-ps pulses, and
optical coherence tomography needing pulses in the 10-fs regime at very modest average powers.
Received: 29 June 2000 / Published online: 6 December 2000 相似文献
58.
59.
Recent developments in asymmetric aziridination 总被引:1,自引:0,他引:1
Hélène Pellissier Author Vitae 《Tetrahedron》2010,66(8):1509-94
60.
不同氛围下烟草的热裂解行为研究 总被引:2,自引:0,他引:2
烟丝分别在He和空气环境中于600、700、800、900、1 000 ℃下进行热裂解,裂解产物用GC-MS进行在线检测,研究了烟丝样品分别在惰性和有氧氛围中不同温度下的热裂解行为.数据表明,烟丝在He气和空气中热裂解时的产物有较大差异,He气下的裂解产物以烯烃、苯和苯系物为主;在空气下裂解的主要产物为酮、醛、醇、酸和酯等羰基化合物.有氧氛围有益于异戊二烯和1,3-丁二烯的生成,但在一定程度上抑制了酚类物质的产生.在惰性和有氧氛围下,随着温度的升高,多环芳烃化合物的产生量均进一步增加.He氛围下得到的裂解产物类型接近卷烟燃烧时的热解区,而空气氛围下得到的裂解产物类型接近燃烧区. 相似文献