Rotational Temperature Estimation of CO at High Temperatures by Graphical Methods Using FT-IR Spectrometry

Abstract

Rotational temperatures are obtained from gas-phase Fourier transformed infrared spectra of CO with the use of graphical methods over the temperature range 302 to 773 K. Peak absorbances of individual rovibrational transitions are corrected for instrumental distortion and are then fit to a Boltzmann distribution to obtain the rotational temperature of the gas. A solution to the convolution integral for FT-IR spectrometry is obtained by numerical integration. The equation relating observed peak absorbance, A_obs, to true peak absorbance, A_pm, ranging from one to five true peak absorbance units for triangularly apodized spectra is:

$A_{p m} \propto A_{o b s}^{1.818} ρ^{1.748}$

where the resolution parameter, ρ, is equal to 1/(2Δγ_m), γ_m is the half-width at half-height (HWHH) of the absorption line in question, and Δ is the maximum optical retardation of the interferometer (here equal to 1 cm). In all cases, temperatures obtained by graphical analysis yielded gas temperatures within 10% of the actual temperatures. Experiments were also conducted to determine the CO rotational temperature in a premixed, low-pressure (64 Torr) CH₄/N₂O flame. CO temperatures for the premixed flame ranged from 1500 to 1700 K, indicating a large transferral of heat from the flame to the burner chamber.

Keywords

Flame spectroscopy Infrared Analytical methods

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References

Infrared Methods for Gaseous Measurements, Wormhoudt

Joda

, Ed. (Marcel Dekker, New York, 1985); Gross

L. A.

and Griffiths

P. R

, J. Quant. Spectrosc. Radiat. Transfer 39, 131 (1988); Gross

L. A.

and Griffiths

P. R

, J. Quant. Spectrosc. Radiat. Transfer 39, 463 (1988); Griffiths

P. R.

and de Haseth

J. A

, Fourier Transform Infrared Spectrometry (John Wiley and Sons, New York, 1986).

Herzberg

, Spectra of Diatomic Molecules (Van Nostrand, New York, 1950).

Anderson

R. J.

and Griffiths

P. R

, Anal. Chem. 47, 2339 (1975).

Bracewell

R. N.

, The Fourier Transform and Its Applications (McGraw-Hill, New York, 1986), Chap. 3.

Anderson

R. J.

and Griffiths

P. R

, J. Quant. Spectrosc. Radiat. Transfer 17, 393 (1977); also see Ref. 3.

Herman

and Wallis

R. F

, J. Chem. Phys. 23, 637 (1955).

Eng

R. S.

and Mantz

A. W

, J. Mol. Spec. 74, 331 (1979).

Bouanich

J. P.

Farrenq

and Brobeck

, Can. J. Phys. 61, 192 (1983); Nakazawa

and Tanaka

, J. Quant. Spectrosc. Radiat. Transfer 28, 409 (1982).

Gross

L. A.

Griffiths

P. R.

and Sun

J. N.-P

, “Temperature Measurement by Infrared Spectrometry,” in Infrared Methods for Gaseous Measurements, Wormhoudt

Joda

, Ed. (Marcel Dekker, New York, 1985), p. 98.

10.

Seshadri

K. S.

and Jones

R. Norman

, Spectrochim. Acta 19, 1013 (1963).

11.

Hunt

R. H.

Toth

R. A.

and Plyler

E. K

, J. Chem. Phys. 49, 3909 (1968); Bouanich

J. P.

and Brodbeck

, J. Quant. Spectrosc. Radiat Transfer 13, 1 (1973).

12.

Thomas

G. B.

, Calculus and Analytical Geometry (Addison-Wesley, Reading, Massachusetts, 1966).

13.

Rank

D. H.

St. Pierre

A. G.

and Wiggins

T. A

, J. Mol. Spec. 18, 418 (1965); Johns

J. W. C.

McKellar

A. R. W.

and Weitz

, J. Mol. Spec. 51, 539 (1974).

14.

Cvetanovic

R. J.

and Singleton

D. L

, Int. J. Chem. Kin. IX, 481 (1977).

15.

Herzberg

, Spectra of Diatomic Molecules (Van Nostrand, New York, 1950).

16.

Thorne

L. R.

and Smith

O. I

, “The Structure of Cyanogen-NO₂ Premixed Flames,” delivered at the 25th JANNAF Combustion Meeting, Huntsville, Alabama (1988).