Abstract

A tunable diode laser has been applied in optical Stark-modulated absorption spectroscopy to provide spatially resolved concentration measurements of CO. A cw IR probe beam from the diode laser was crossed with a nonresonant high-intensity beam from a Nd:YAG laser to generate a Stark-induced change in absorption in the crossing volume. The optical Stark-modulated absorption spectra were calculated showing the influence of experimental parameters including partial pressure of CO, total absorption path length, and intensity of the perturbing beam. The technique was demonstrated in a premixed atmospheric CH4–air flame and in a room temperature absorption cell, and good agreement was found between experiment and theoretical calculations. Thus far a spatial resolution of 0.5 cm has been achieved for time-averaged measurements of CO flame mole fractions of a few percent. Further improvements in the system should enable measurements of CO levels approaching 0.1% in flames with spatial resolution in the mm range and temporal resolution of 10 nsec.

© 1983 Optical Society of America

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References

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  1. R. K. Hanson, P. A. Kuntz, C. H. Kruger, Appl. Opt. 16, 2045 (1977).
    [CrossRef] [PubMed]
  2. S. M. Schoenung, R. K. Hanson, Combust. Sci. Technol. 24, 227 (1981).
    [CrossRef]
  3. P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
    [CrossRef]
  4. R. K. Hanson, P. K. Falcone, Appl. Opt. 17, 2477 (1978).
    [CrossRef] [PubMed]
  5. R. K. Hanson, Appl. Opt. 19, 482 (1980).
    [CrossRef] [PubMed]
  6. S. M. Schoenung, R. K. Hanson, Appl. Opt. 21, 1767 (1982).
    [CrossRef] [PubMed]
  7. S. M. Schoenung, R. K. Hanson, in Nineteenth Symposium (International) on Combustion, (Combustion Institute, Pittsburgh, 1983), p. 449.
  8. P. L. Varghese, R. K. Hanson, J. Quant. Spectrosc. Radiat. Transfer 26, 339 (1981).
    [CrossRef]
  9. L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
    [CrossRef]
  10. R. L. Farrow, L. A. Rahn, Opt. Lett. 6, 108 (1981).
    [CrossRef] [PubMed]
  11. C. H. Townes, A. Schawlow, Microwave Spectroscopy (McGraw-Hill, New York1955).
  12. R. L. Farrow, Appl. Opt. 21, 4183 (1982).
    [CrossRef] [PubMed]
  13. A. M. Bonch-Bruevich, V. A. Khodovoi, Sov. Phys. Usp. 10, 637 (1968).
    [CrossRef]
  14. J. E. M. Goldsmith, R. L. Farrow, Opt. Lett. 7, 215 (1982).
    [CrossRef] [PubMed]
  15. H.-J. Hartmann, A. Laubereau, Appl. Opt. 20, 4259 (1981).
    [CrossRef] [PubMed]

1983

P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
[CrossRef]

1982

1981

H.-J. Hartmann, A. Laubereau, Appl. Opt. 20, 4259 (1981).
[CrossRef] [PubMed]

S. M. Schoenung, R. K. Hanson, Combust. Sci. Technol. 24, 227 (1981).
[CrossRef]

R. L. Farrow, L. A. Rahn, Opt. Lett. 6, 108 (1981).
[CrossRef] [PubMed]

P. L. Varghese, R. K. Hanson, J. Quant. Spectrosc. Radiat. Transfer 26, 339 (1981).
[CrossRef]

1980

L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
[CrossRef]

R. K. Hanson, Appl. Opt. 19, 482 (1980).
[CrossRef] [PubMed]

1978

1977

1968

A. M. Bonch-Bruevich, V. A. Khodovoi, Sov. Phys. Usp. 10, 637 (1968).
[CrossRef]

Bonch-Bruevich, A. M.

A. M. Bonch-Bruevich, V. A. Khodovoi, Sov. Phys. Usp. 10, 637 (1968).
[CrossRef]

Falcone, P. K.

P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
[CrossRef]

R. K. Hanson, P. K. Falcone, Appl. Opt. 17, 2477 (1978).
[CrossRef] [PubMed]

Farrow, R. L.

Goldsmith, J. E. M.

Hanson, R. K.

P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
[CrossRef]

S. M. Schoenung, R. K. Hanson, Appl. Opt. 21, 1767 (1982).
[CrossRef] [PubMed]

S. M. Schoenung, R. K. Hanson, Combust. Sci. Technol. 24, 227 (1981).
[CrossRef]

P. L. Varghese, R. K. Hanson, J. Quant. Spectrosc. Radiat. Transfer 26, 339 (1981).
[CrossRef]

R. K. Hanson, Appl. Opt. 19, 482 (1980).
[CrossRef] [PubMed]

R. K. Hanson, P. K. Falcone, Appl. Opt. 17, 2477 (1978).
[CrossRef] [PubMed]

R. K. Hanson, P. A. Kuntz, C. H. Kruger, Appl. Opt. 16, 2045 (1977).
[CrossRef] [PubMed]

S. M. Schoenung, R. K. Hanson, in Nineteenth Symposium (International) on Combustion, (Combustion Institute, Pittsburgh, 1983), p. 449.

Hartmann, H.-J.

Khodovoi, V. A.

A. M. Bonch-Bruevich, V. A. Khodovoi, Sov. Phys. Usp. 10, 637 (1968).
[CrossRef]

Koszykowski, M. L.

L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
[CrossRef]

Kruger, C. H.

P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
[CrossRef]

R. K. Hanson, P. A. Kuntz, C. H. Kruger, Appl. Opt. 16, 2045 (1977).
[CrossRef] [PubMed]

Kuntz, P. A.

Laubereau, A.

Mattern, P. L.

L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
[CrossRef]

Rahn, L. A.

R. L. Farrow, L. A. Rahn, Opt. Lett. 6, 108 (1981).
[CrossRef] [PubMed]

L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
[CrossRef]

Schawlow, A.

C. H. Townes, A. Schawlow, Microwave Spectroscopy (McGraw-Hill, New York1955).

Schoenung, S. M.

S. M. Schoenung, R. K. Hanson, Appl. Opt. 21, 1767 (1982).
[CrossRef] [PubMed]

S. M. Schoenung, R. K. Hanson, Combust. Sci. Technol. 24, 227 (1981).
[CrossRef]

S. M. Schoenung, R. K. Hanson, in Nineteenth Symposium (International) on Combustion, (Combustion Institute, Pittsburgh, 1983), p. 449.

Townes, C. H.

C. H. Townes, A. Schawlow, Microwave Spectroscopy (McGraw-Hill, New York1955).

Varghese, P. L.

P. L. Varghese, R. K. Hanson, J. Quant. Spectrosc. Radiat. Transfer 26, 339 (1981).
[CrossRef]

Appl. Opt.

Combust. Sci. Technol.

S. M. Schoenung, R. K. Hanson, Combust. Sci. Technol. 24, 227 (1981).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer

P. K. Falcone, R. K. Hanson, C. H. Kruger, J. Quant. Spectrosc. Radiat. Transfer 29, 205 (1983).
[CrossRef]

P. L. Varghese, R. K. Hanson, J. Quant. Spectrosc. Radiat. Transfer 26, 339 (1981).
[CrossRef]

Opt. Lett.

Phys. Rev. Lett.

L. A. Rahn, R. L. Farrow, M. L. Koszykowski, P. L. Mattern, Phys. Rev. Lett. 45, 620 (1980).
[CrossRef]

Sov. Phys. Usp.

A. M. Bonch-Bruevich, V. A. Khodovoi, Sov. Phys. Usp. 10, 637 (1968).
[CrossRef]

Other

C. H. Townes, A. Schawlow, Microwave Spectroscopy (McGraw-Hill, New York1955).

S. M. Schoenung, R. K. Hanson, in Nineteenth Symposium (International) on Combustion, (Combustion Institute, Pittsburgh, 1983), p. 449.

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Figures (9)

Fig. 1
Fig. 1

Simple model for beam geometry used to calculate the optical Stark-shifted spectra.

Fig. 2
Fig. 2

Calculated optical Stark spectrum of the P(20) CO line for different Stark shifts ΔΩ; see Eq. (1): temperature, 300 K; total pressure, 0.2 atm; CO partial pressure, 0.2 atm; total absorption length, 0.4 cm; interaction length, 0.4 cm; FWHM = 0.024 cm−1.

Fig. 3
Fig. 3

Calculated optical Stark spectrum of the P(20) CO line for different CO partial pressures; see Eq. (1): temperature, 300 K; total pressure, 0.2 atm; total absorption length, 0.4 cm; interaction length, 0.4 cm; Stark shift, −0.05 cm−1; FWHM = 0.024 cm−1.

Fig. 4
Fig. 4

Calculated optical Stark spectrum of the P(20) CO line for different total absorption lengths; see Eq. (1): temperature, 300 K; total presure, 0.2 atm; CO partial pressure, 0.2 atm; interaction length, 0.4 cm; Stark shift, −0.05 cm−1; FWHM = 0.024 cm−1.

Fig. 5
Fig. 5

Experimental setup for optical Stark-modulated absorption spectroscopy.

Fig. 6
Fig. 6

Measured and calculated optical Stark spectrum of the P(20) CO line using an absorption cell with ptotal = 0.025 atm: temperature, 293 K; CO partial pressure, 0.0002 atm; total absorption length, 7.0 cm; interaction length, 0.5 cm; Nd:YAG laser energy, 300 mJ; Stark shift, −0.022 cm−1; FWHM = 0.0060 cm−1.

Fig. 7
Fig. 7

Measured and calculated optical Stark spectrum of the P(20) CO line using an absorption cell with ptotal = 0.250 atm; temperature, 293 K; CO partial pressure, 0.0002 atm; total absorption length, 7.0 cm; interaction length, 0.5 cm; Nd:YAG laser energy, 300 mJ; Stark shift, −0.026 cm−1; FWHM = 0.027 cm−1.

Fig. 8
Fig. 8

Measured optical Stark shift for different energies of the perturbing Nd:YAG laser.

Fig. 9
Fig. 9

Measured and calculated optical Stark spectrum of the P(20) CO line using a premixed CH4/air flame: temperature, 1400 K; total pressure, 1 atm; CO partial pressure, 0.05 atm; total absorption length, 1.6 cm; interaction length, 0.5 cm; Nd:YAG laser energy, 430 mJ; Stark shift, −0.035 cm−1; FWHM = 0.046 cm−1.

Tables (1)

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Table I Experimental Parameter in the Flame Measurements

Equations (5)

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Δ i ( ω ) I ac ( ω ) I 0 - I ( ω ) I 0 = exp [ - S ϕ ( ω - ω 0 ) p i ( L tot - L ) ] · exp { - S ϕ [ ω - ( ω 0 + Δ Ω ) ] p i L } - exp { - S ϕ ( ω - ω 0 ) p i L tot } ,
Δ i ( ω ) = S p i L { ϕ ( ω - ω 0 ) - ϕ [ ω - ( ω 0 + Δ Ω ) ] } .
i signal = R f Δ i ( ω ) P 0 ,
Q signal = i signal · Δ t .
Q noise = 2 e R P 0 Δ f · Δ T ,

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