Flames laser spectroscopy

Experiments are currently in progress to measure CO and NO concentrations in a flat flame burner by diode laser spectroscopy. Comparative measurements are also being made using microprobe sampling with subsequent analysis by non-dispersive infrared and chemiluminescent techniques. Some preliminary laser absorption results for CO are reported here initial results for NO have been published separately (4). Also reported are initial data for collision halfwidths in combustion gases. 

Smith, J. R., "Rayleigh Temperature Profiles in a Hydrogen Diffusion Flame," Proceedings of SPIE Vol 158 Laser Spectroscopy (1978) p. 84-90. 

Sappey, A. D. "Wavelength-Multiplexed Diode Laser Spectroscopy for Closed Loop Combustion Control and Optimization." Paperpresented atthe American-Japanese Flame Research Committees International Symposium, Waikaloa, HI, 2007. 

The energy required to produce spectral emission can be provided in several ways, including discharge tubes, flames, electric arcs, electric sparks, plasmas, and lasers. The first two, discharge tubes and flames, are not discussed here. Flames are treated in Chapter 9 (Flame Emission Spectroscopy) and discharge tubes are discussed in Chapter 10 (Atomic Absorption Spectroscopy). 

J.C. Travis, Analytical optogalvanic spectroscopy in flames, in Analytical Laser Spectroscopy, ed. by S. Martellucci, A.N. Chester (Plenum, New York, 1985), p. 213 D. King, P. Schenck, K. Smyth, J. Travis, Direct calibration of laser wavelength and bandwidth using the optogalvanic effect in hollow cathode Itimps. Appl. Opt. 16,2617 (1977)... 

V. Hefter, K. Bergmann, Spectroscopic detection methods, in Atomic and Molecular Beam Methods, vol. 1, ed. by G. Scoles (Oxford Univ. Press, New York, 1988), p. 193 J.E.M. Goldsmith, Recent advances in flame diagnostics using fluorescence and ionisation techniques, in Laser Spectroscopy VIII, ed. by S. Svanbeig, W. Persson. Springer Ser. Opt. Sci., vol. 55 (Springer, Berlin, 1987), p. 337... 

J.C. Travis Analytical optogalvanic spectroscopy in flames . In Analytical Laser Spectroscopy, ed. by S. Martellucci, A.N. Chester (Rlenum, New York 1985) p.213... 

Using pulsed lasers and gated detection electronics, Raman measurements can also be performed for major species in flames that do not contain too many particles. Temperature measurements can then also be made using the Stokes/anti-Stokes signal asymmetry or the occurrence of slightly displaced Stokes hot-bands as discussed in Sect.4.4.1. Flame Raman spectroscopy is discussed in further detail in [10.36,37]. 

N.S. Bergano, P.A. Janimaagi, M.M. Salour, J.H. Bechtel Picosecond laser-spectroscopy measurement of hydroxyl fluorescence lifetime in flames. Opt. Lett.8, 443 (1983)... 

There are, however, several advantages to using TDLs for measurement of gas-phase flame species. These include high resolution (typically better than lxl0 cm" ), good spatial resolution (200 to 1 mm), reasonable output power ( 1 mW), and the ability to scan over their spectral range on a millisecond or better timescale. Probably the most widely studied molecular flame species by tunable diode laser spectroscopy is CO. In addition to the reasons for study outlined above in the discussion of broadband source methods, CO possesses several fundamental (v = 0-l) and hot-band transitions (v = 1-2, V = 2-3) which occur within several line widths (approximately 0.05 cm" ) of each other. At room temperature, populations of states from which hot-band transitions occur are very low. However, at flame temperatures, populations of vibrational states other than the v = 0 state may become appreciable. When temperatures (and also species concentrations) are calculated from simultaneous measurement of a fundamental and a hot-band transition, the technique is referred to as two-line thermometry. 

Tunable diode laser spectroscopy is also used for detection of many trace gas species in flames and in flame environments. The method used for measurements of small amounts of gases (often to the ppb range) relies on modulation spectroscopy using... 

An interesting variation of Raman spectroscopy is coherent anti-Stokes Raman spectroscopy (CARS) (99). If two laser beams, with angular frequencies CO and CO2 are combined in a material, and if cjj — is close to a Raman active frequency of the material, then radiation at a new frequency CJ3 = 2cJ2 — may be produced. Detection of this radiation can be used to characterize the material. Often one input frequency is fixed and the other frequency, from a tunable laser, varied until matches the Raman frequency. CARS has the capabiHty for measurements in flames, plasmas, and... 

Daily, J.W., Laser induced fluorescence spectroscopy in flames. Prog. Energy Combust. Sci., 23,133,1997. 

Goldman, A. et al.. Fiber laser intracavity absorption spectroscopy of ammonia and hydrogen cyanide in low pressure hydrocarbon flames, Chem. Phys. Lett., 423, 147, 2006. 

Scherer, J.J. et al.. Determination of methyl radical concentrations in a methane/air flame by infrared cavity ringdown laser absorption spectroscopy,. Chem. Phys., 107, 6196,1997. 

Schoemaecker Moreau, C. et al.. Two-color laser-induced incandescence and cavity ring-down spectroscopy for sensitive and quantitative imaging of soot and PAHs in flames, Appl. Phys. B, 78,485,2004. 

Dreyer, C.B., Spuler, S.M., and Linne, M., Calibration of laser induced fluorescence of the OH radical by cavity ringdown spectroscopy in premixed atmospheric pressure flames. Combust. Sci. Tech., 171,163, 2001. 

Flame Photometry and Gas Chromatography (CyTerra) -Aerodynamic Particle Size and Shape Analysis (BIRAL) -Flow Cytometry (Luminex, LLNL) -Semiconductor-Based Ultraviolet Light (DARPA) -Polymer Fluorochrome (Echo Technology) -Laser-Induced Breakdown Spectroscopy -Raman Scattering -Infrared Absorption -Terahertz Spectroscopy -UV LIDAR... 

Schoenung, S. M., and R. K. Hanson. 1981. CO and temperature measurements in a flat flame by laser absorption spectroscopy and probe techniques. Combustion Science Technology 24 227-37. 

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