Abstract

The strengths of more than 1600 lines of CH4 have been measured in the spectral interval between 5500 and 6150 cm−1 at room temperature and reduced temperatures. The variation of the measured strengths allows the energy of the lower state of the transition to be determined empirically using the temperature dependence of the methane partition function and the Boltzmann factor for the energy level populations. An error analysis, based on assumed errors in the strength and temperature measurements, is included. The average measured uncertainty in J is 0.2.

© 1990 Optical Society of America

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References

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  1. J. S. Margolis, “Measured Line Positions and Strengths of Methane Between 5500 and 6180 cm−1,” Appl. Opt. 27, 4038–4050 (1988).
    [CrossRef] [PubMed]
  2. J. Ballard, W. B. Johnston, “Self-Broadened Widths and Absolute Strengths of 12CH4 Lines in the 1310–1370 cm−1 Region,” J. Quant. Spectrosc. Radiat. Transfer. 36, 365–371 (1986).
    [CrossRef]
  3. V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
    [CrossRef]
  4. K. Fox, “On the Rotational Partition Function for Tetrahedral Molecules,” J. Quant. Spectrosc. Radiat. Transfer. 10, 1335–1342 (1970).
    [CrossRef]
  5. G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
    [CrossRef]

1988

1986

J. Ballard, W. B. Johnston, “Self-Broadened Widths and Absolute Strengths of 12CH4 Lines in the 1310–1370 cm−1 Region,” J. Quant. Spectrosc. Radiat. Transfer. 36, 365–371 (1986).
[CrossRef]

1983

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

1975

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

1970

K. Fox, “On the Rotational Partition Function for Tetrahedral Molecules,” J. Quant. Spectrosc. Radiat. Transfer. 10, 1335–1342 (1970).
[CrossRef]

Amiot, C.

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

Ballard, J.

J. Ballard, W. B. Johnston, “Self-Broadened Widths and Absolute Strengths of 12CH4 Lines in the 1310–1370 cm−1 Region,” J. Quant. Spectrosc. Radiat. Transfer. 36, 365–371 (1986).
[CrossRef]

Dang-Nhu, M.

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

Fox, K.

K. Fox, “On the Rotational Partition Function for Tetrahedral Molecules,” J. Quant. Spectrosc. Radiat. Transfer. 10, 1335–1342 (1970).
[CrossRef]

Fridovich, B.

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

Guelachvili, G.

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

Johnston, W. B.

J. Ballard, W. B. Johnston, “Self-Broadened Widths and Absolute Strengths of 12CH4 Lines in the 1310–1370 cm−1 Region,” J. Quant. Spectrosc. Radiat. Transfer. 36, 365–371 (1986).
[CrossRef]

Jones, G. D.

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

Malathy Devi, V.

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

Margolis, J. S.

Poussigue, G.

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

Snyder, D. G. S.

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

Tarrago, G.

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

Appl. Opt.

J. Mol. Spectrosc.

V. Malathy Devi, B. Fridovich, G. D. Jones, D. G. S. Snyder, “Strengths and Lorentz Broadening Coefficients for Spectral Lines in the ν3 and ν2 + ν4 bands of 12CH4 and 13CH4,” J. Mol. Spectrosc. 97, 333–342 (1983).
[CrossRef]

G. Tarrago, M. Dang-Nhu, G. Poussigue, G. Guelachvili, C. Amiot, “The Ground State of Methane 12CH4 Through the Forbidden Lines of the ν3 Band,” J. Mol. Spectrosc. 57, 246–263 (1975).
[CrossRef]

J. Quant. Spectrosc. Radiat. Transfer.

J. Ballard, W. B. Johnston, “Self-Broadened Widths and Absolute Strengths of 12CH4 Lines in the 1310–1370 cm−1 Region,” J. Quant. Spectrosc. Radiat. Transfer. 36, 365–371 (1986).
[CrossRef]

K. Fox, “On the Rotational Partition Function for Tetrahedral Molecules,” J. Quant. Spectrosc. Radiat. Transfer. 10, 1335–1342 (1970).
[CrossRef]

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Figures (2)

Fig. 1
Fig. 1

Percentage error in the determination of E″ as a function of E″: The solid line is for an error of 2 K in the 180 K-temperature measurement and the dashed line is for an error of 2 K in the 200 K-temperature measurement. Both curves correspond to an error of 1 K in the 296 K-temperature measurement.

Fig. 2
Fig. 2

Uncertainty of the effective J value determination is shown for an uncertainty of 5% in the strength measurement at both room and reduced temperatures.

Tables (2)

Tables Icon

Table I Empirical Values Calculated for Ground State Energies of Transitions In Methane

Tables Icon

Table II Empirical J″ Determinations for some Lines Tentatively Assigned to 2ν4 ± ν3

Equations (3)

Equations on this page are rendered with MathJax. Learn more.

S ( J , T ) = ν S 0 Q - 1 ( T ) H ( J ) exp [ - E ( J ) / k T ] ,
S ( J , T 1 ) / S ( J , T 2 ) = ( T 2 / T 1 ) 3 / 2 exp [ - E / k ( T 1 - 1 - T 2 - 1 ) ] .
E = { 1.5 ln ( T 2 / T 1 ) - ln [ S ( T 1 ) / S ( T 2 ) ] } 0.69541 [ T 1 T 2 / ( T 2 - T 1 ) ] .

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