Abstract

Two-dimensional imaging of CO concentration in combustion gases is demonstrated using two-photon-excited planar laser-induced fluorescence. A quantitative model is presented for the simultaneous two-photon excitation of several rotational transitions of the B1+X1+ system and the subsequent visible fluorescence (B1+A1Π). The model is verified by comparison of predicted and measured excitation spectra and of temperature-corrected relative fluorescence measurements to standard probe measurements of the center line CO distribution in a CO–air diffusion flame. In addition, CO imaging experiments in a premixed methane–air flame indicate the production of C2 by laser photodissociation of acetylene.

© 1987 Optical Society of America

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References

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  1. M. Goeppert-Mayer, “Uber Elementarakte mit Zwei Quantensprungen,” Ann. Phys. 9, 273 (1931).
    [CrossRef]
  2. R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
    [CrossRef]
  3. W. Demtroder, Laser Spectroscopy (Springer-Verlag, Berlin, 1982), p. 436.
  4. D. M. Friedrich, W. M. McClain, “Two-Photon Molecular Electronic Spectroscopy,” Ann. Rev. Phys. Commun. 31, 559 (1980).
    [CrossRef]
  5. N. Bloembergen, M. D. Levenson, “Doppler-Free Two-Photon Absorption Spectroscopy,” in High-Resolution Laser Spectroscopy, Topics in Applied Physics, Vol. 13, K. Shimoda, Ed. (Springer-Verlag, Berlin, 1976), p. 318.
    [CrossRef]
  6. M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
    [CrossRef]
  7. A. W. Miziolek, M. A. DeWilde, “Multiphoton Photochemical and Collisional Effects During Oxygen–Atom Flame Detection,” Opt. Lett. 9, 390 (1984).
    [CrossRef] [PubMed]
  8. R. P. Lucht, J. T. Salmon, G. B. King, D. W. Sweeney, N. M. Laurendeau, “Two-Photon-Excited Fluorescence Measurement of Hydrogen Atoms in Flames,” Opt. Lett. 8, 365 (1983).
    [CrossRef] [PubMed]
  9. D. R. Crosley, G. P. Smith, “Two Photon Spectroscopy of the A2∑+–X2Πi System of OH,” J. Chem. Phys. 79, 4764 (1983).
    [CrossRef]
  10. J. E. M. Goldsmith, N. M. Laurendeau, “Two-Photon-Excited Fluorescence Measurements of OH Concentration in a Hydrogen–Oxygen Flame,” Appl. Opt. 25, 276 (1986).
    [CrossRef] [PubMed]
  11. M. Aldeń, H. M. Hertz, S. Svanberg, S. Wallin, “Imaging Laser-Induced Fluorescence of Oxygen Atoms in a Flame,” Appl. Opt. 23, 3255 (1984).
    [CrossRef]
  12. M. Aldeń, S. Wallin, W. Wendt, “Application of Two-Photon Absorption for Detection of CO in Combustion Gases,” Appl. Phys. B 33, 205 (1984).
    [CrossRef]
  13. J. Haumann, J. M. Seitzman, R. K. Hanson, “Two-Photon Digital Imaging of CO in Combustion Flows Using Planar Laser-Induced Fluorescence,” Opt. Lett. 11, 776 (1986).
    [CrossRef] [PubMed]
  14. R. K. Hanson, “Combustion Diagnostics: Planar Flowfield Imaging,” in Twenty-First Symposium (International) on Combustion (The Combustion Institute, Pittsburgh, PA, 1987).
  15. G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
    [CrossRef]
  16. J. T. Salmon, N. M. Laurendeau, “Quenching-Independent Fluorescence Measurements of Atomic Hydrogen With Photo-ionization Controlled-Loss Spectroscopy,” Opt. Lett. 11, 419 (1986).
    [CrossRef] [PubMed]
  17. K. P. Huber, G. Herzberg, Constants of Diatomic Molecules (Van Nostrand-Rheinhold, New York, 1979), p. 160.
  18. S. G. Tilford, J. D. Simmons, “Carbon Monoxide Spectral Atlas,” J. Phys. Chem. Ref. Data 1, 147 (1972).
    [CrossRef]
  19. J. Humlicek, “An Efficient Method for Evaluation of the Complex Probability Function: The Voigt Function and its Derivatives,” J. Quant. Spectrosc. Radiat. Transfer 21, 309 (1979).
    [CrossRef]
  20. G. Kychakoff, R. D. Howe, R. K. Hanson, “Quantitative Flow Visualization Technique for Measurements in Combustion Gases,” Appl. Opt. 23, 704 (1984).
    [CrossRef] [PubMed]
  21. J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
    [CrossRef]
  22. J. E. M. Goldsmith, Sandia National Laboratories, Combustion Research Facility; private communication.
  23. W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
    [CrossRef]
  24. D. A. Greenhalgh, “RECLAS: Resonant-Enhanced CARS From C2 Produced by Laser Ablation of Soot Particles,” Appl. Opt. 22, 1128 (1983).
    [CrossRef] [PubMed]
  25. J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
    [CrossRef]
  26. B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
    [CrossRef]

1986 (3)

1984 (4)

1983 (4)

R. P. Lucht, J. T. Salmon, G. B. King, D. W. Sweeney, N. M. Laurendeau, “Two-Photon-Excited Fluorescence Measurement of Hydrogen Atoms in Flames,” Opt. Lett. 8, 365 (1983).
[CrossRef] [PubMed]

D. R. Crosley, G. P. Smith, “Two Photon Spectroscopy of the A2∑+–X2Πi System of OH,” J. Chem. Phys. 79, 4764 (1983).
[CrossRef]

G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
[CrossRef]

D. A. Greenhalgh, “RECLAS: Resonant-Enhanced CARS From C2 Produced by Laser Ablation of Soot Particles,” Appl. Opt. 22, 1128 (1983).
[CrossRef] [PubMed]

1982 (2)

B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
[CrossRef]

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

1981 (1)

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

1980 (2)

J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
[CrossRef]

D. M. Friedrich, W. M. McClain, “Two-Photon Molecular Electronic Spectroscopy,” Ann. Rev. Phys. Commun. 31, 559 (1980).
[CrossRef]

1979 (1)

J. Humlicek, “An Efficient Method for Evaluation of the Complex Probability Function: The Voigt Function and its Derivatives,” J. Quant. Spectrosc. Radiat. Transfer 21, 309 (1979).
[CrossRef]

1978 (1)

J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
[CrossRef]

1974 (1)

R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
[CrossRef]

1972 (1)

S. G. Tilford, J. D. Simmons, “Carbon Monoxide Spectral Atlas,” J. Phys. Chem. Ref. Data 1, 147 (1972).
[CrossRef]

1931 (1)

M. Goeppert-Mayer, “Uber Elementarakte mit Zwei Quantensprungen,” Ann. Phys. 9, 273 (1931).
[CrossRef]

Alden, M.

M. Aldeń, S. Wallin, W. Wendt, “Application of Two-Photon Absorption for Detection of CO in Combustion Gases,” Appl. Phys. B 33, 205 (1984).
[CrossRef]

M. Aldeń, H. M. Hertz, S. Svanberg, S. Wallin, “Imaging Laser-Induced Fluorescence of Oxygen Atoms in a Flame,” Appl. Opt. 23, 3255 (1984).
[CrossRef]

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

Baronavski, A. P.

J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
[CrossRef]

Bloembergen, N.

N. Bloembergen, M. D. Levenson, “Doppler-Free Two-Photon Absorption Spectroscopy,” in High-Resolution Laser Spectroscopy, Topics in Applied Physics, Vol. 13, K. Shimoda, Ed. (Springer-Verlag, Berlin, 1976), p. 318.
[CrossRef]

Craig, B. B.

B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
[CrossRef]

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

Crosley, D. R.

D. R. Crosley, G. P. Smith, “Two Photon Spectroscopy of the A2∑+–X2Πi System of OH,” J. Chem. Phys. 79, 4764 (1983).
[CrossRef]

Demtroder, W.

W. Demtroder, Laser Spectroscopy (Springer-Verlag, Berlin, 1982), p. 436.

DeWilde, M. A.

Donnely, V. M.

J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
[CrossRef]

Edner, H.

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

Faust, W. L.

B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
[CrossRef]

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

Friedrich, D. M.

D. M. Friedrich, W. M. McClain, “Two-Photon Molecular Electronic Spectroscopy,” Ann. Rev. Phys. Commun. 31, 559 (1980).
[CrossRef]

Goeppert-Mayer, M.

M. Goeppert-Mayer, “Uber Elementarakte mit Zwei Quantensprungen,” Ann. Phys. 9, 273 (1931).
[CrossRef]

Goldberg, L. S.

B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
[CrossRef]

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

Goldsmith, J. E. M.

Grafstrom, P.

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

Greenhalgh, D. A.

Halpern, J. B.

J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
[CrossRef]

Hanson, R. K.

Haumann, J.

Hertz, H. M.

Herzberg, G.

K. P. Huber, G. Herzberg, Constants of Diatomic Molecules (Van Nostrand-Rheinhold, New York, 1979), p. 160.

Hochstrasser, R. M.

R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
[CrossRef]

Howe, R. D.

Huber, K. P.

K. P. Huber, G. Herzberg, Constants of Diatomic Molecules (Van Nostrand-Rheinhold, New York, 1979), p. 160.

Humlicek, J.

J. Humlicek, “An Efficient Method for Evaluation of the Complex Probability Function: The Voigt Function and its Derivatives,” J. Quant. Spectrosc. Radiat. Transfer 21, 309 (1979).
[CrossRef]

King, G. B.

Kychakoff, G.

Laurendeau, N. M.

Levenson, M. D.

N. Bloembergen, M. D. Levenson, “Doppler-Free Two-Photon Absorption Spectroscopy,” in High-Resolution Laser Spectroscopy, Topics in Applied Physics, Vol. 13, K. Shimoda, Ed. (Springer-Verlag, Berlin, 1976), p. 318.
[CrossRef]

Loge, G. W.

G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
[CrossRef]

Lucht, R. P.

McClain, W. M.

D. M. Friedrich, W. M. McClain, “Two-Photon Molecular Electronic Spectroscopy,” Ann. Rev. Phys. Commun. 31, 559 (1980).
[CrossRef]

McDonald, J. R.

J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
[CrossRef]

Miziolek, A. W.

Salmon, J. T.

Seitzman, J. M.

Simmons, J. D.

S. G. Tilford, J. D. Simmons, “Carbon Monoxide Spectral Atlas,” J. Phys. Chem. Ref. Data 1, 147 (1972).
[CrossRef]

Smith, G. P.

D. R. Crosley, G. P. Smith, “Two Photon Spectroscopy of the A2∑+–X2Πi System of OH,” J. Chem. Phys. 79, 4764 (1983).
[CrossRef]

Sung, H. W.

R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
[CrossRef]

Svanberg, S.

M. Aldeń, H. M. Hertz, S. Svanberg, S. Wallin, “Imaging Laser-Induced Fluorescence of Oxygen Atoms in a Flame,” Appl. Opt. 23, 3255 (1984).
[CrossRef]

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

Sweeney, D. W.

Tiee, J. J.

G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
[CrossRef]

Tilford, S. G.

S. G. Tilford, J. D. Simmons, “Carbon Monoxide Spectral Atlas,” J. Phys. Chem. Ref. Data 1, 147 (1972).
[CrossRef]

Wallenstein, R.

J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
[CrossRef]

Wallin, S.

M. Aldeń, S. Wallin, W. Wendt, “Application of Two-Photon Absorption for Detection of CO in Combustion Gases,” Appl. Phys. B 33, 205 (1984).
[CrossRef]

M. Aldeń, H. M. Hertz, S. Svanberg, S. Wallin, “Imaging Laser-Induced Fluorescence of Oxygen Atoms in a Flame,” Appl. Opt. 23, 3255 (1984).
[CrossRef]

Wampler, F. B.

G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
[CrossRef]

Weiss, R. G.

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

Wendt, W.

M. Aldeń, S. Wallin, W. Wendt, “Application of Two-Photon Absorption for Detection of CO in Combustion Gases,” Appl. Phys. B 33, 205 (1984).
[CrossRef]

Wessel, J. E.

R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
[CrossRef]

Zacharias, H.

J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
[CrossRef]

Ann. Phys. (1)

M. Goeppert-Mayer, “Uber Elementarakte mit Zwei Quantensprungen,” Ann. Phys. 9, 273 (1931).
[CrossRef]

Ann. Rev. Phys. Commun. (1)

D. M. Friedrich, W. M. McClain, “Two-Photon Molecular Electronic Spectroscopy,” Ann. Rev. Phys. Commun. 31, 559 (1980).
[CrossRef]

Appl. Opt. (4)

Appl. Phys. B (1)

M. Aldeń, S. Wallin, W. Wendt, “Application of Two-Photon Absorption for Detection of CO in Combustion Gases,” Appl. Phys. B 33, 205 (1984).
[CrossRef]

Chem. Phys. (1)

J. R. McDonald, A. P. Baronavski, V. M. Donnely, “Multi-photon-Vacuum-Ultraviolet Laser Photodissociation of Acetylene: Emission from Electronically Excited Fragments,” Chem. Phys. 33, 161 (1978).
[CrossRef]

Chem. Phys. Lett. (1)

W. L. Faust, L. S. Goldberg, B. B. Craig, R. G. Weiss, “Time-Resolved C2 Swan Emission From Short-Pulse UV Fragmentation of CO: Evidence For Two C2 Formation Mechanisms,” Chem. Phys. Lett. 83, 265 (1981).
[CrossRef]

J. Chem. Phys. (4)

D. R. Crosley, G. P. Smith, “Two Photon Spectroscopy of the A2∑+–X2Πi System of OH,” J. Chem. Phys. 79, 4764 (1983).
[CrossRef]

B. B. Craig, W. L. Faust, L. S. Goldberg, “UV Short-Pulse Fragmentation of Isotopically Labeled Acetylene: Studies of Emission With Subnanosecond Resolution,” J. Chem. Phys. 76, 5014 (1982).
[CrossRef]

R. M. Hochstrasser, J. E. Wessel, H. W. Sung, “Two-Photon Excitation Spectrum of Benzene in the Gas Phase and the Crystal,” J. Chem. Phys. 60, 317 (1974).
[CrossRef]

G. W. Loge, J. J. Tiee, F. B. Wampler, “Multiphoton Induced Fluorescence and Ionization of Carbon Monoxide (B1∑+),” J. Chem. Phys. 79, 196 (1983).
[CrossRef]

J. Mol. Spectrosc. (1)

J. B. Halpern, H. Zacharias, R. Wallenstein, “Rotational Line Strengths in Two- and Three-Photon Transitions in Diatomic Molecules,” J. Mol. Spectrosc. 79, 1 (1980).
[CrossRef]

J. Phys. Chem. Ref. Data (1)

S. G. Tilford, J. D. Simmons, “Carbon Monoxide Spectral Atlas,” J. Phys. Chem. Ref. Data 1, 147 (1972).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer (1)

J. Humlicek, “An Efficient Method for Evaluation of the Complex Probability Function: The Voigt Function and its Derivatives,” J. Quant. Spectrosc. Radiat. Transfer 21, 309 (1979).
[CrossRef]

Opt. Commun. (1)

M. Aldeń, H. Edner, P. Grafstrom, S. Svanberg, “Two-Photon Excitation of Atomic Oxygen in Flames,” Opt. Commun. 42, 244 (1982).
[CrossRef]

Opt. Lett. (4)

Other (5)

R. K. Hanson, “Combustion Diagnostics: Planar Flowfield Imaging,” in Twenty-First Symposium (International) on Combustion (The Combustion Institute, Pittsburgh, PA, 1987).

W. Demtroder, Laser Spectroscopy (Springer-Verlag, Berlin, 1982), p. 436.

N. Bloembergen, M. D. Levenson, “Doppler-Free Two-Photon Absorption Spectroscopy,” in High-Resolution Laser Spectroscopy, Topics in Applied Physics, Vol. 13, K. Shimoda, Ed. (Springer-Verlag, Berlin, 1976), p. 318.
[CrossRef]

K. P. Huber, G. Herzberg, Constants of Diatomic Molecules (Van Nostrand-Rheinhold, New York, 1979), p. 160.

J. E. M. Goldsmith, Sandia National Laboratories, Combustion Research Facility; private communication.

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Figures (9)

Fig. 1
Fig. 1

Energy level diagram of CO showing states involved in the excitation and detection process for two-photon LIF of CO at 230 nm.

Fig. 2
Fig. 2

Four-level model for two-photon LIF of CO where levels 1 and 3 are single rovibronic levels of the X and B electronic states, respectively; level 2 represents all rovibronic levels in the A state which are radiatively coupled (within the detector bandwidth) to level 3; and level 4 represents states to which the CO molecule can be ionized with an additional 230-nm photon. The Wij terms are the stimulated transition rate coefficients, and the Tij terms represent the spontaneous emission and collisional quenching terms (Tij = Aij+ Qij).

Fig. 3
Fig. 3

Theoretical (relative) two-photon absorption coefficient, k(ν1 + ν2,T) and excitation spectrum, Np(ν,T) for the Q-branch of the CO B1+(v′ = 0) ← X1+(v″ = 0) transition at 300 K [from Eqs. (6) and (7)].

Fig. 4
Fig. 4

Calculated temperature dependence of the two-photon-excited CO fluorescence for fixed CO mole fraction and for excitation at 230.08 and 230.10 nm.

Fig. 5
Fig. 5

Schematic of the experimental apparatus used for the single-point measurements and the 2-D imaging experiments: DC, doubling crystal; MC, mixing crystal; SL, spherical lens; M1, M2, cylindrical mirrors. The translational and rotational degrees of freedom for the mirrors in the multipass cell are indicated by arrows.

Fig. 6
Fig. 6

Two-photon excitation spectra for the Q-branch of the CO B1+(v′ = 0) ← X1+(v″ = 0) transition from 230.06 to 230.11 nm at 300 K (recorded in a CO jet) and 700 K (recorded in a CO–air diffusion flame). The open circles and filled squares are experimental points, and the solid and dashed curves are theoretical predictions [Eq. (7)] normalized (by a multiplicative constant) to fit the experimental data at the peak values.

Fig. 7
Fig. 7

Single-shot image (2.5 × 3 cm) of CO fluorescence (230.10-nm excitation) measured in a laminar atmospheric-pressure CO–air diffusion flame, stabilized above the exit of a 6mm diameter fuel tube. The original digitization of 256 levels has been reduced to six levels in this presentation.

Fig. 8
Fig. 8

Comparison of LIF and probe measurements of the CO mole fraction profile along the center line of the CO–air diffusion flame depicted in Fig. 7. The two-photon LIF signals of Fig. 7 were converted to mole fraction measurements using a measured temperature profile and the model results shown in Fig. 4.

Fig. 9
Fig. 9

Three (nonsimultaneous) single-shot images (2.2 × 2.7 cm) acquired in an atmospheric-pressure fuel-rich premixed methane–air flame: (a) 100 μs exposure of flame emission; (b) 1-μs image of the fluorescence (CO + C2) produced by laser excitation at 230.10 nm; (c) 1-μs image of the C2 fluorescence (from photodissociation of C2H2) excited by a 230.50-nm laser pulse. For (b) and (c), all camera system parameters (e.g., intensifier gain) and the nominal pulse energies were fixed.

Equations (7)

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R f = N tot F 1 W 13 ( 2 v ) ( 1 / 4 π ) A 32 / [ j ( A 3 j + Q 3 j ) + W 34 ( i ) ] ,
W 13 ( 2 ν ) = ( I / h c ν 0 ) 2 σ 2 ν - - ϕ 2 ν ( ν 1 + ν 2 ) × ϕ L ( ν 1 ) ϕ L ( ν 2 ) d ν 1 d ν 2 ,
W 34 ( i ) = ( I / h c ν 0 ) σ i - ϕ i ( ν ) ϕ L ( ν ) d ν ,
- ϕ L ( ν ) d ν = - ϕ i ( ν ) d ν = - - ϕ 2 ν ( ν 1 + ν 2 ) d ν 1 d ν 2 = 1.
R c ( ν 0 ) = η ( Ω / 4 π ) V c N c o [ - - k ( ν 1 , ν 2 , T ) ϕ L ( ν 1 ) ϕ L ( ν 2 ) d ν 1 d ν 2 ] × ( i / h c ν 0 ) 2 A A + Q + C i I / h c ν 0 ,
k ( ν 1 , ν 2 , T ) = J J [ σ v v ( S J J / 2 J + 1 ) F v J ϕ 2 ν ( ν 1 + ν 2 ] ,
N p ( ν 0 ) = η ( Ω / 4 π ) V c ( E / h c ν 0 ) ( A / C i ) N CO × [ - - k ( ν 1 , ν 2 , T ) ϕ L ( ν 1 ) ϕ L ( ν 2 ) d ν 1 d ν 2 ] ,

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