Abstract

The pressure-modulated near-infrared emission spectrum of a gas consists of a set of vibration-rotation bands. The intensity of the emitted radiation is a rapidly varying function of frequency. The transmission of this radiation through various gas samples has been investigated for absorbing atomspheric gases such as carbon dioxide, carbon monoxide, nitrous oxide, and methane; the effects of pressure-broadening of spectral lines by inert gases such as argon and nitrogen have been considered. The transmittance of radiant power has been shown to depend on the composition of the emitting sample and the compression ratio employed as well as on the composition of the absorbing sample. Possible application of pressure-modulation techniques to atmospheric transmission studies is suggested.

© 1962 Optical Society of America

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References

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  1. R. R. Patty and D. Williams, J. Opt. Soc. Am. 51, 1351 (1961).
    [Crossref]
  2. R. R. Patty and D. Williams, J. Opt. Soc. Am. 52, 543 (1962).
    [Crossref]
  3. See W. M. Elasasser, Harvard Meteorological Studies No. 6, Harvard University, 1942, for discussion of weak and strong lines and G. N. Plass, J. Opt. Soc. Am. 50, 868 (1960) for discussion of weak and strong bands.
    [Crossref]

1962 (1)

1961 (1)

Elasasser, W. M.

See W. M. Elasasser, Harvard Meteorological Studies No. 6, Harvard University, 1942, for discussion of weak and strong lines and G. N. Plass, J. Opt. Soc. Am. 50, 868 (1960) for discussion of weak and strong bands.
[Crossref]

Patty, R. R.

Williams, D.

J. Opt. Soc. Am. (2)

Other (1)

See W. M. Elasasser, Harvard Meteorological Studies No. 6, Harvard University, 1942, for discussion of weak and strong lines and G. N. Plass, J. Opt. Soc. Am. 50, 868 (1960) for discussion of weak and strong bands.
[Crossref]

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Figures (8)

Fig. 1
Fig. 1

Plots of percent transmittance versus absorber concentration in path comparing the results for a conventional source with a “black” and “non-black” gaseous source. Pure nitrous oxide used as source and absorbing sample. 2:1 compression ratio. 12.6-cm absorption cell.

Fig. 2
Fig. 2

Plots of percent transmittance versus partial pressure of sample in path for three sources of radiation. 2:1 compression ratio. 12.6-cm absorption cell.

Fig. 3
Fig. 3

Spectral radiance of nitrous oxide viewed through methane (upper curves), and spectral radiance of methane viewed through nitrous oxide (lower curves) for the partial pressure p and the total pressure P shown. Compression ratio 5:1.

Fig. 4
Fig. 4

Spectral radiance of carbon monoxide viewed through various absorber concentrations and total pressures of carbon monoxide placed in the beam for the 2143-cm−1 band. Source is 4 cm CO + argon to 15 cm Hg. 2:1 compression ratio. 12.6-cm absorption cell.

Fig. 5
Fig. 5

Plots of the absorptance versus partial pressure of carbon monoxide placed in the path. The source is 4 cm Hg of CO plus argon to 15 cm Hg. 2:1 compression ratio. 12.6-cm absorption cell.

Fig. 6
Fig. 6

Spectral radiance of CO2 viewed through various CO2 samples and plot showing the dependence of the absorptance for the entire band on the compression ratio of the source which is 4 cm Hg of CO2 plus argon to 15 cm Hg. 12.6-cm absorption cell.

Fig. 7
Fig. 7

Spectra of the 1285-cm−1 and 1167-cm−1 N2O bands showing the effect of adding a nonabsorbing gas to various absorber concentrations w, where w is the product of the partial pressure of absorber in atmospheres and the cell length. The source is 4 cm Hg of N2O plus argon to 10 cm Hg. Compression ratio 2:1. 6.3-cm absorption cell.

Fig. 8
Fig. 8

Plots showing the dependence of the transmittance on the total pressure of the absorber for strong and weak bands. The source is 4 cm Hg of N2O plus argon to 10 cm Hg and the absorber is N2O. 2:1 compression ratio. 6.3-cm absorption cell.

Equations (1)

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D 0 d x D d x D 0 d x ,