Abstract

Water continuum CO2 laser absorption spectra are reported for temperatures between 27 and −10°C. The continuum is found to possess a negative temperature coefficient. The results obtained suggest that the magnitude of this temperature coefficient increases with increasing water pressure and decreasing temperature. The temperature coefficients between 27 and 10°C for air mixtures containing 3.0- and 7.5-Torr water vapor are −2.0 ± 0.4 and −2.9 ± 0.5%/°C, respectively. For mixtures with 3.0-Torr water the 10–0°C temperature coefficient is −7.7 ± 0.2%/°C. The temperature and water pressure dependencies observed for the continuum suggest that while both collisional broadening and water dimer mechanisms contribute to the continuum, the dimer mechanism is more important over this temperature range.

© 1983 Optical Society of America

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  1. K. M. Haught, J. A. Dowling, Opt. Lett. 1, 121 (1977).
    [CrossRef] [PubMed]
  2. R. E. Roberts, J. E. A. Selby, L. M. Biberman, Appl. Opt. 15, 2085 (1976).
    [CrossRef] [PubMed]
  3. K. O. White, W. R. Watkins, C. W. Bruce, R. E. Meredith, F. G. Smith, Appl. Opt. 17, 2711 (1978).
    [CrossRef] [PubMed]
  4. J. H. McCoy, D. B. Rensch, R. K. Long, Appl. Opt. 8, 1471 (1969).
    [CrossRef] [PubMed]
  5. D. E. Burch, “Investigation of the Absorption of Infrared Radiation by Atmospheric Gases,” Semi-Annual Technical Report, contract F19628-69-C-0263, Aeronutronic Report U-4784 (Jan.1970).
  6. K. J. Bignell, Q. J. R. Meteorol. Soc. 96, 390 (1970).
    [CrossRef]
  7. V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).
  8. R. J. Nordstrom, M. E. Thomas, J. C. Peterson, E. K. Damon, R. K. Long, Appl. Opt. 17, 2724 (1978).
    [CrossRef] [PubMed]
  9. D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).
  10. G. P. Montgomery, Appl. Opt. 17, 2299 (1978).
    [CrossRef] [PubMed]
  11. G. L. Loper, M. A. O'Neill, J. A. Gelbwachs, “Below Room Temperature Water Continuum Absorption Within the 8–12 μm Atmosphere Transmission Window,” Aerospace Corp. Report TR-0083 (8494)-1 (1983).
  12. M. S. Shumate, R. T. Menzies, J. S. Margolis, L.-G. Rosengren, Appl. Opt. 15, 2480 (1976).
    [CrossRef] [PubMed]
  13. J. C. Peterson, “A Study of Water Vapor Absorption at CO2 Laser Frequencies Using a Differential Spectrophone and White Cell,” Dissertation, Ohio State U., (June1978).
  14. J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
    [CrossRef] [PubMed]
  15. M. E. Thomas, “Tropospheric Water Vapor Absorption in the Infrared Window Regions,” Dissertation, Ohio State U., (Aug.1979).
  16. R. J. Nordstrom, M. E. Thomas, “The Water Vapor Continuum as Wings of Strong Absorption Lines,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).
  17. S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).
  18. S. H. Suck, J. L. Kassner, Y. Yamaguchi, Appl. Opt. 18, 2609 (1979).
    [CrossRef] [PubMed]
  19. S. H. Suck, A. E. Wetmore, T. S. Chen, J. L. Kassner, Appl. Opt. 21, 1610 (1982).
    [CrossRef] [PubMed]
  20. H. R. Carlon, Appl. Opt. 17, 3192 (1978);Infrared Phys. 19, 49, 549 (1979);H. R. Carlon, C. S. Harden, Appl. Opt. 19, 1776 (1980).
    [CrossRef] [PubMed]
  21. T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
    [CrossRef]
  22. G. L. Loper, A. R. Calloway, M. A. Stamps, J. A. Gelbwachs, Appl. Opt. 19, 2726 (1980).
    [CrossRef] [PubMed]
  23. J. S. Ryan, M. H. Hubert, R. A. Crane, Appl. Opt. 22, 711 (1983).
    [CrossRef] [PubMed]
  24. R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).
  25. A pure linear dependence is observed only when the absorption strength of the local water line is significantly greater than the absorption strength of the underlying water continuum.
  26. D. E. Burch, D. A. Gryvnak, G. H. Piper, “Infrared Absorption by H2O and N2O,” contract F19628-73-C-0011, Aeronutronic Report U-6026 (July1973);D. E. Burch, D. A. Gryvnak, F. J. Gates, “Continuum Absorption by H2O Between 300 and 825 cm−1,” AFCRL-TR-74-0377, Aeronutronic Report U-6095 (Sept.1974).
  27. The so-called self-broadening coefficient Cs(λ,T) plotted vs temperature in Fig. 8 is most often defined in the literature through the relationabs(λ,T)=Cs(λ,T)wH2O[pH2O+γ(λ,T)(P−pH2O)].Here abs(λ,T) is the water continuum absorption coefficient at a particular wavelength and temperature, wH2O is the density of water vapor in units of molecules/cm3, pH2O is the water partial pressure, P is the total pressure in units of atmospheres, and γ(λ,T) = Cf(λ,T)/Cs(λ,T) is the foreign-broadening to self-broadening coefficient ratio.
  28. The water dimer model of Suck and co-workers18,19 predicts that the water continuum absorption strength varies with temperature by the factorT−3∏i=16{exp(−hυi/2kT)/[1−exp(−hυi/kT)]}exp(−ΔH°/RT),where h is Planck's constant, k is Boltzmann's constant, and the υi correspond to the frequencies of the six intermolecular vibrational modes of the water dimer. Here ΔH° is the water vapor dimer electronic binding energy at 0 K, while R is the gas law constant, and T is the temperature in kelvins. On the basis of molecular orbital calculations, Suck and co-workers19 chose the binding energy to be −6.5 kcal/mole. The dimer intermolecular frequencies predicted by Owicki et al.29 (593, 496, 189, 168, 161, and 98 cm−1) have been assumed by Suck et al.
  29. J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
    [CrossRef]
  30. The self-broadening coefficient Cs(λ,T) and foreign-broadening coefficient Cf(λ,T) defined in Ref. 27 can be calculated from the linear and quadratic coefficients a(λ,T) and b(λ,T) in Table II through the relationshipsCf(λ,T)=a(λ,T)P(pH2OwH2O),Cs(λ,T)=pH2OwH2O[b(λ,T)+a(λ,T)/P].The Cs values shown at 27, 10, 0, and −10°C in Fig. 8 were calculated from averages of Cs (λ,T) data determined within the laser 10.4-μm band P-branch, where local water absorption line contributions are negligible.
  31. For most atmospheric conditions, the magnitude of the continuum absorption is primarily governed by its water pressure quadratic component. From the linear and quadratic coefficients in Table II, it is observed that the quadratic water pressure component contributes predominantly to the total water absorption coefficient at 27 and 10°C for water pressures greater than ∼3 and 2 Torr, respectively. For lower temperatures, the quadratic component would be the major contributor to the continuum at even lower pressures.
  32. R. R. Patty, G. M. Russwurm, W. A. McClenny, D. R. Morgan, Appl. Opt. 13, 2850 (1974).
    [CrossRef] [PubMed]
  33. A. Mayer, J. Comera, H. Charpentier, C. Jaussaud, Appl. Opt. 17, 391 (1978).
    [CrossRef] [PubMed]
  34. U. Persson, B. Marthinsson, J. Johansson, S. T. Eng, Appl. Opt. 19, 1711 (1980).
    [CrossRef] [PubMed]
  35. E. H. Christy, K. H. Faller, in Second Joint Conference on Sensing of Environmental Pollutants, 10– 12 Dec. 1973, Washington, D.C., paper 23.
  36. R. J. Brewer, C. W. Bruce, J. L. Mater, Appl. Opt. 21, 4092 (1982).
    [CrossRef] [PubMed]

1983 (1)

1982 (2)

1980 (2)

1979 (2)

1978 (5)

1977 (1)

1976 (2)

1975 (3)

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
[CrossRef]

T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
[CrossRef]

1974 (1)

1970 (1)

K. J. Bignell, Q. J. R. Meteorol. Soc. 96, 390 (1970).
[CrossRef]

1969 (1)

Alt, R. L.

D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).

Arefev, V. N.

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

Benedict, W. S.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

Biberman, L. M.

Bignell, K. J.

K. J. Bignell, Q. J. R. Meteorol. Soc. 96, 390 (1970).
[CrossRef]

Brewer, R. J.

Bruce, C. W.

Burch, D. E.

D. E. Burch, “Investigation of the Absorption of Infrared Radiation by Atmospheric Gases,” Semi-Annual Technical Report, contract F19628-69-C-0263, Aeronutronic Report U-4784 (Jan.1970).

D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

D. E. Burch, D. A. Gryvnak, G. H. Piper, “Infrared Absorption by H2O and N2O,” contract F19628-73-C-0011, Aeronutronic Report U-6026 (July1973);D. E. Burch, D. A. Gryvnak, F. J. Gates, “Continuum Absorption by H2O Between 300 and 825 cm−1,” AFCRL-TR-74-0377, Aeronutronic Report U-6095 (Sept.1974).

Calfee, R. F.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

Calloway, A. R.

Carlon, H. R.

Charpentier, H.

Chen, T. S.

Christy, E. H.

E. H. Christy, K. H. Faller, in Second Joint Conference on Sensing of Environmental Pollutants, 10– 12 Dec. 1973, Washington, D.C., paper 23.

Clough, S. A.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Comera, J.

Crane, R. A.

Damon, E. K.

Davies, R.

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Deaton, T. F.

T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
[CrossRef]

Depatie, D. A.

T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
[CrossRef]

Dianov-Klokov, V. I.

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

Dowling, J. A.

Eng, S. T.

Faller, K. H.

E. H. Christy, K. H. Faller, in Second Joint Conference on Sensing of Environmental Pollutants, 10– 12 Dec. 1973, Washington, D.C., paper 23.

Fox, K.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

Gamache, R.

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Garing, J. S.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

Gelbwachs, J. A.

G. L. Loper, A. R. Calloway, M. A. Stamps, J. A. Gelbwachs, Appl. Opt. 19, 2726 (1980).
[CrossRef] [PubMed]

G. L. Loper, M. A. O'Neill, J. A. Gelbwachs, “Below Room Temperature Water Continuum Absorption Within the 8–12 μm Atmosphere Transmission Window,” Aerospace Corp. Report TR-0083 (8494)-1 (1983).

Gryvnak, D. A.

D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).

D. E. Burch, D. A. Gryvnak, G. H. Piper, “Infrared Absorption by H2O and N2O,” contract F19628-73-C-0011, Aeronutronic Report U-6026 (July1973);D. E. Burch, D. A. Gryvnak, F. J. Gates, “Continuum Absorption by H2O Between 300 and 825 cm−1,” AFCRL-TR-74-0377, Aeronutronic Report U-6095 (Sept.1974).

Haught, K. M.

Hubert, M. H.

Jaussaud, C.

Johansson, J.

Kassner, J. L.

Kneizys, F. X.

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Long, R. K.

Loper, G. L.

G. L. Loper, A. R. Calloway, M. A. Stamps, J. A. Gelbwachs, Appl. Opt. 19, 2726 (1980).
[CrossRef] [PubMed]

G. L. Loper, M. A. O'Neill, J. A. Gelbwachs, “Below Room Temperature Water Continuum Absorption Within the 8–12 μm Atmosphere Transmission Window,” Aerospace Corp. Report TR-0083 (8494)-1 (1983).

Margolis, J. S.

Marthinsson, B.

Mater, J. L.

Mayer, A.

McClatchey, R. A.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

McClenny, W. A.

McCoy, J. H.

Menzies, R. T.

Meredith, R. E.

Montgomery, G. P.

Morgan, D. R.

Nordstrom, R. J.

J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
[CrossRef] [PubMed]

R. J. Nordstrom, M. E. Thomas, J. C. Peterson, E. K. Damon, R. K. Long, Appl. Opt. 17, 2724 (1978).
[CrossRef] [PubMed]

R. J. Nordstrom, M. E. Thomas, “The Water Vapor Continuum as Wings of Strong Absorption Lines,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

O'Neill, M. A.

G. L. Loper, M. A. O'Neill, J. A. Gelbwachs, “Below Room Temperature Water Continuum Absorption Within the 8–12 μm Atmosphere Transmission Window,” Aerospace Corp. Report TR-0083 (8494)-1 (1983).

Owicki, J. C.

J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
[CrossRef]

Patty, R. R.

Persson, U.

Peterson, J. C.

J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
[CrossRef] [PubMed]

R. J. Nordstrom, M. E. Thomas, J. C. Peterson, E. K. Damon, R. K. Long, Appl. Opt. 17, 2724 (1978).
[CrossRef] [PubMed]

J. C. Peterson, “A Study of Water Vapor Absorption at CO2 Laser Frequencies Using a Differential Spectrophone and White Cell,” Dissertation, Ohio State U., (June1978).

Piper, G. H.

D. E. Burch, D. A. Gryvnak, G. H. Piper, “Infrared Absorption by H2O and N2O,” contract F19628-73-C-0011, Aeronutronic Report U-6026 (July1973);D. E. Burch, D. A. Gryvnak, F. J. Gates, “Continuum Absorption by H2O Between 300 and 825 cm−1,” AFCRL-TR-74-0377, Aeronutronic Report U-6095 (Sept.1974).

Radionov, V. F.

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

Rensch, D. B.

Roberts, R. E.

Rosengren, L.-G.

Rothman, L. S.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

Russwurm, G. M.

Ryan, J. S.

Scheraga, H. A.

J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
[CrossRef]

Selby, J. E. A.

Shipman, L. L.

J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
[CrossRef]

Shumate, M. S.

Sizov, N. I.

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

Smith, F. G.

Stamps, M. A.

Suck, S. H.

Thomas, M. E.

J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
[CrossRef] [PubMed]

R. J. Nordstrom, M. E. Thomas, J. C. Peterson, E. K. Damon, R. K. Long, Appl. Opt. 17, 2724 (1978).
[CrossRef] [PubMed]

M. E. Thomas, “Tropospheric Water Vapor Absorption in the Infrared Window Regions,” Dissertation, Ohio State U., (Aug.1979).

R. J. Nordstrom, M. E. Thomas, “The Water Vapor Continuum as Wings of Strong Absorption Lines,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Tipping, R.

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

Walker, T. W.

T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
[CrossRef]

Watkins, W. R.

Wetmore, A. E.

White, K. O.

Yamaguchi, Y.

Zgonc, D. K.

D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).

Appl. Opt. (16)

R. E. Roberts, J. E. A. Selby, L. M. Biberman, Appl. Opt. 15, 2085 (1976).
[CrossRef] [PubMed]

K. O. White, W. R. Watkins, C. W. Bruce, R. E. Meredith, F. G. Smith, Appl. Opt. 17, 2711 (1978).
[CrossRef] [PubMed]

J. H. McCoy, D. B. Rensch, R. K. Long, Appl. Opt. 8, 1471 (1969).
[CrossRef] [PubMed]

R. J. Nordstrom, M. E. Thomas, J. C. Peterson, E. K. Damon, R. K. Long, Appl. Opt. 17, 2724 (1978).
[CrossRef] [PubMed]

G. P. Montgomery, Appl. Opt. 17, 2299 (1978).
[CrossRef] [PubMed]

M. S. Shumate, R. T. Menzies, J. S. Margolis, L.-G. Rosengren, Appl. Opt. 15, 2480 (1976).
[CrossRef] [PubMed]

J. C. Peterson, M. E. Thomas, R. J. Nordstrom, E. K. Damon, R. K. Long, Appl. Opt. 18, 834 (1979).
[CrossRef] [PubMed]

S. H. Suck, J. L. Kassner, Y. Yamaguchi, Appl. Opt. 18, 2609 (1979).
[CrossRef] [PubMed]

S. H. Suck, A. E. Wetmore, T. S. Chen, J. L. Kassner, Appl. Opt. 21, 1610 (1982).
[CrossRef] [PubMed]

H. R. Carlon, Appl. Opt. 17, 3192 (1978);Infrared Phys. 19, 49, 549 (1979);H. R. Carlon, C. S. Harden, Appl. Opt. 19, 1776 (1980).
[CrossRef] [PubMed]

G. L. Loper, A. R. Calloway, M. A. Stamps, J. A. Gelbwachs, Appl. Opt. 19, 2726 (1980).
[CrossRef] [PubMed]

J. S. Ryan, M. H. Hubert, R. A. Crane, Appl. Opt. 22, 711 (1983).
[CrossRef] [PubMed]

R. R. Patty, G. M. Russwurm, W. A. McClenny, D. R. Morgan, Appl. Opt. 13, 2850 (1974).
[CrossRef] [PubMed]

A. Mayer, J. Comera, H. Charpentier, C. Jaussaud, Appl. Opt. 17, 391 (1978).
[CrossRef] [PubMed]

U. Persson, B. Marthinsson, J. Johansson, S. T. Eng, Appl. Opt. 19, 1711 (1980).
[CrossRef] [PubMed]

R. J. Brewer, C. W. Bruce, J. L. Mater, Appl. Opt. 21, 4092 (1982).
[CrossRef] [PubMed]

Appl. Phys. Lett. (1)

T. F. Deaton, D. A. Depatie, T. W. Walker, Appl. Phys. Lett. 26, 300 (1975).
[CrossRef]

J. Phys. Chem. (1)

J. C. Owicki, L. L. Shipman, H. A. Scheraga, J. Phys. Chem. 79, 1794 (1975).
[CrossRef]

Opt. Lett. (1)

Opt. Spectrosc. (1)

V. N. Arefev, V. I. Dianov-Klokov, V. F. Radionov, N. I. Sizov, Opt. Spectrosc. 39, 560 (1975);V. N. Arefev, V. I. Dianov-Klokov, Opt. Spectrosc. 42, 488 (1977).

Q. J. R. Meteorol. Soc. (1)

K. J. Bignell, Q. J. R. Meteorol. Soc. 96, 390 (1970).
[CrossRef]

Other (15)

D. A. Gryvnak, D. E. Burch, R. L. Alt, D. K. Zgonc, “Infrared Absorption by CH4, H2O, and CO2,” AFGL-TR-76-0246, Final Report, contract F19628-76-C-0067, Aeronutronic Report U-6275 (Dec.1977).

D. E. Burch, “Investigation of the Absorption of Infrared Radiation by Atmospheric Gases,” Semi-Annual Technical Report, contract F19628-69-C-0263, Aeronutronic Report U-4784 (Jan.1970).

M. E. Thomas, “Tropospheric Water Vapor Absorption in the Infrared Window Regions,” Dissertation, Ohio State U., (Aug.1979).

R. J. Nordstrom, M. E. Thomas, “The Water Vapor Continuum as Wings of Strong Absorption Lines,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

S. A. Clough, F. X. Kneizys, R. Davies, R. Gamache, R. Tipping, “Theoretical Line Shape for H2O Vapor; Application to the Continuum,” in Atmospheric Water Vapor, A. Deepak, T. D. Wilkerson, L. H. Ruhnke, Eds. (Academic, New York, 1980).

J. C. Peterson, “A Study of Water Vapor Absorption at CO2 Laser Frequencies Using a Differential Spectrophone and White Cell,” Dissertation, Ohio State U., (June1978).

G. L. Loper, M. A. O'Neill, J. A. Gelbwachs, “Below Room Temperature Water Continuum Absorption Within the 8–12 μm Atmosphere Transmission Window,” Aerospace Corp. Report TR-0083 (8494)-1 (1983).

The self-broadening coefficient Cs(λ,T) and foreign-broadening coefficient Cf(λ,T) defined in Ref. 27 can be calculated from the linear and quadratic coefficients a(λ,T) and b(λ,T) in Table II through the relationshipsCf(λ,T)=a(λ,T)P(pH2OwH2O),Cs(λ,T)=pH2OwH2O[b(λ,T)+a(λ,T)/P].The Cs values shown at 27, 10, 0, and −10°C in Fig. 8 were calculated from averages of Cs (λ,T) data determined within the laser 10.4-μm band P-branch, where local water absorption line contributions are negligible.

For most atmospheric conditions, the magnitude of the continuum absorption is primarily governed by its water pressure quadratic component. From the linear and quadratic coefficients in Table II, it is observed that the quadratic water pressure component contributes predominantly to the total water absorption coefficient at 27 and 10°C for water pressures greater than ∼3 and 2 Torr, respectively. For lower temperatures, the quadratic component would be the major contributor to the continuum at even lower pressures.

E. H. Christy, K. H. Faller, in Second Joint Conference on Sensing of Environmental Pollutants, 10– 12 Dec. 1973, Washington, D.C., paper 23.

R. A. McClatchey, W. S. Benedict, S. A. Clough, D. E. Burch, R. F. Calfee, K. Fox, L. S. Rothman, J. S. Garing, AFCRL Atmospheric Absorption Line Parameters Compilation, AFCRL-TR-73-0096, Bedford, Mass. (1973).

A pure linear dependence is observed only when the absorption strength of the local water line is significantly greater than the absorption strength of the underlying water continuum.

D. E. Burch, D. A. Gryvnak, G. H. Piper, “Infrared Absorption by H2O and N2O,” contract F19628-73-C-0011, Aeronutronic Report U-6026 (July1973);D. E. Burch, D. A. Gryvnak, F. J. Gates, “Continuum Absorption by H2O Between 300 and 825 cm−1,” AFCRL-TR-74-0377, Aeronutronic Report U-6095 (Sept.1974).

The so-called self-broadening coefficient Cs(λ,T) plotted vs temperature in Fig. 8 is most often defined in the literature through the relationabs(λ,T)=Cs(λ,T)wH2O[pH2O+γ(λ,T)(P−pH2O)].Here abs(λ,T) is the water continuum absorption coefficient at a particular wavelength and temperature, wH2O is the density of water vapor in units of molecules/cm3, pH2O is the water partial pressure, P is the total pressure in units of atmospheres, and γ(λ,T) = Cf(λ,T)/Cs(λ,T) is the foreign-broadening to self-broadening coefficient ratio.

The water dimer model of Suck and co-workers18,19 predicts that the water continuum absorption strength varies with temperature by the factorT−3∏i=16{exp(−hυi/2kT)/[1−exp(−hυi/kT)]}exp(−ΔH°/RT),where h is Planck's constant, k is Boltzmann's constant, and the υi correspond to the frequencies of the six intermolecular vibrational modes of the water dimer. Here ΔH° is the water vapor dimer electronic binding energy at 0 K, while R is the gas law constant, and T is the temperature in kelvins. On the basis of molecular orbital calculations, Suck and co-workers19 chose the binding energy to be −6.5 kcal/mole. The dimer intermolecular frequencies predicted by Owicki et al.29 (593, 496, 189, 168, 161, and 98 cm−1) have been assumed by Suck et al.

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Figures (10)

Fig. 1
Fig. 1

CO2 laser photoacoustic detection system.

Fig. 2
Fig. 2

CO2 laser absorption spectra of water–air mixtures containing 7.5-Torr water vapor.

Fig. 3
Fig. 3

CO2 laser absorption spectra of water-air mixtures containing 3.0-Torr water vapor.

Fig. 4
Fig. 4

CO2 laser absorption spectra of water-air mixtures containing water vapor.

Fig. 5
Fig. 5

Dependence of absorption coefficients of 760-Torr total pressure water-air mixtures vs water partial pressure at CO2 laser 10.4-μm band P(16) line. Solid lines correspond to absorption predicted from a[P(16),10°C], b[P(16),10°C] and a[P(16),27°C], b[P(16),27°C] coefficients in Table II.

Fig. 6
Fig. 6

Comparison of water pressure linear coefficients as a function of CO2 laser wavelength at 10 and 27°C.

Fig. 7
Fig. 7

Comparison of water pressure quadratic coefficients as a function of CO2 laser wavelength at 10 and 27°C.

Fig. 8
Fig. 8

Experimental compared to predicted (see Ref. 28) temperature dependence of the water pressure quadratic component of the 8–12-μm water continuum absorption. The dimer intermolecular frequencies predicted by Owicki et al.29 have been assumed in the dimer model used here. The dimer model predicts a Cs value of 2.0 × 10−22 molecules−1 cm2 atm−1 at 23°C. This value is based on the 1.7 × 10−6-cm−1 absorption strength estimated by Suck et al.19 at 10 μm for mixtures containing 14-Torr water at 23°C. This Cs value has been increased by a factor of 1.3 here to better match the absolute values of Cs measured between 100 and −10°C. The predicted dimer concentration temperature dependence, however, is identical to that of Suck et al.19

Fig. 9
Fig. 9

Experimental compared to predicted temperature dependence of water absorption peak at the CO2 laser 10.4-μm band R(20) line. El represents assumed lower state energy level.

Fig. 10
Fig. 10

Water partial pressure dependence at 10°C of water near line center absorption at the CO2 laser 10.4-μm band R(20) line. Solid line corresponds to absorption predicted from a[R(20),10°C] and b[R(20),10°C] coefficients in Table II.

Tables (3)

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Table I Laser 10.4-μm Band Absorption Coefficients (in units of 10−6 cm−1) of Water-Vapor-Air Mixtures at Selected Temperatures and Water Partial Pressures a

Tables Icon

Table II Comparison at 27 and 10°C of the Linear and Quadratic Water Pressure Dependence of CO2 Laser Absorption Coefficients for 760-Torr Total Pressure Water-Vapor–Aira Mixtures

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Table III Ethylene Absorption Cross Sections σ (in units of cm−1 atm−1) at Selected CO2 Laser Wavelengths

Equations (11)

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P σ ( n )
P σ ( n ) P σ ( 14 ) ratio
P σ ( n )
P σ ( n )
P σ ( n ) P σ ( 14 ) ratio
P σ ( n )
P σ ( n ) P σ ( 14 ) ratio
P σ ( n ) P σ ( 14 ) ratio
abs(λ,T)=Cs(λ,T)wH2O[pH2O+γ(λ,T)(PpH2O)].
T3i=16{exp(hυi/2kT)/[1exp(hυi/kT)]}exp(ΔH°/RT),
Cf(λ,T)=a(λ,T)P(pH2OwH2O),Cs(λ,T)=pH2OwH2O[b(λ,T)+a(λ,T)/P].

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