Curtis P. Rinsland, V. Malathy Devi, Mary Ann H. Smith, and D. Chris Benner, "Measurements of air-broadened and nitrogen-broadened Lorentz width coefficients and pressure shift coefficients in the ν4 and ν2 bands of 12CH4," Appl. Opt. 27, 631-651 (1988)
Air-broadened and N2-broadened halfwidth and pressure shift coefficients of 294 transitions in the ν4 and ν2 bands of 12CH4 have been measured from laboratory absorption spectra recorded at room temperature with the Fourier transform spectrometer in the McMath solar telescope facility of the National Solar Observatory. Total pressures of up to 551 Torr were employed with absorption paths of 5–150 cm, CH4 volume mixing ratios of 2.6% or less, and resolutions of 0.005 and 0.01 cm−1. A nonlinear least-squares spectral fitting technique has been utilized in the analysis of the twenty-five measured spectra. Lines up to J″ = 18 in the ν4 band and J″ = 15 in the ν2 band have been analyzed.
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Halfwidth coefficients are in cm−1 atm−1 at 296 K. Pressure shift coefficients are in cm−1 atm−1 at about 298 K. Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
1986 HITRAN line parameters compilation3 values.
Measurements with 2 sigma uncertainties (in parentheses) are those of Malathy Devi et al.14 The other values are the N2-broadened width coefficients of Varanasi el al.13
Table III
Halfwidth and Pressure Shift Coefficientsa Measured in the ν2 Band of 12CH4
Halfwidth coefficients are in cm−1 atm−1 at 296 K. Pressure shift coefficients are in cm−1 atm−1 at about 298 K. Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
1986 HITRAN line parameters compilation3 values.
Measurements and 2 sigma uncertainties of Malathy Devi et al.15
Table IV
Comparison of Air-Broadened Halfwidth Coefficients (cm−1 atm−1 at 296 K) Measured in Both the R and P Branches of the ν4 Band
Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
Ratio of the halfwidth coefficient in the R branch to the corresponding value in the P branch.
2 sigma uncertainty in R.
Table V
Mean and Standard Deviation of the Ratio of R- branch to P- branch Air-Broadened Halfwidth Coefficients
Species
Mean
Standard deviation
N
F
0.99
0.04
45
A
0.96
0.02
16
E
1.01
0.09
19
N is the number of transitions measured in both the R and P branches.
Table VI
Mean and Standard Deviation of Halfwidth Coefficient (in cm−1 atm−1 at 296 K) vs |m| Derived from Air-Broadening Measurements in the ν4 and ν2 Bands of 12CH4
|m|
F species
A speciese
E species
Mean
Standard deviation
N
Mean
Standard deviation
N
Mean
Standard deviation
N
0–1.5
0.066
1
0.056
1
2–3.5
0.066
0.002
6
0.066
0.006
2
0.061
0.006
2
4–5.5
0.066
0.003
14
0.063
0.006
4
0.058
0.002
4
6–7.5
0.064
0.003
26
0.061
0.004
12
0.056
0.005
7
8–9.5
0.058
0.003
28
0.058
0.006
10
0.052
0.005
11
10–11.5
0.054
0.006
27
0.053
0.005
12
0.045
0.009
7
12–13.5
0.051
0.004
17
0.052
0.006
9
0.041
0.007
7
14–15.5
0.047
0.007
26
0.044
0.008
9
0.036
0.007
8
16–17.5
0.047
0.005
18
0.044
0.005
7
0.029
0.010
7
18–19.5
0.045
0.004
6
0.039
0.005
4
0.028
0.009
2
N is the number of measured lines.
Table VII
Comparison Between Air-Broadened Halfwidth Coefficients (cm−1 atm−1 at 296 K) Measured in the R Branch of the ν4 Band in this Study and the Calculated Values of Tejwani et al.25
m
Species
Measured
Calculated
Ratio
2
F1
0.0630(10)
0.0606
1.039
3
F2
0.0651(14)
0.0679
0.959
4
F1
0.0668(17)
0.0595
1.123
F2
0.0678(10)
0.0671
1.011
5
F2
0.0641(3)
0.0660
0.972
F1
0.0684(3)
0.0659
1.038
6
F2
0.0652(5)
0.0648
1.007
7
F1
0.0665(8)
0.0645
1.032
Notes: (1) Only lines resulting from a single K state are listed.
Table VIII
Mean and Standard Deviation of Halfwidth Coefficients Obtained In this Study Ratloed to Previously Reported Values
Values in parentheses are 2σ uncertainties in units of the last quoted digit.
Permitted transitions, this study
Permitted transitions from Benner et al.30 ν4 band halfwidth coefficient divided by ν3 band halfwidth coefficient.
Table X
Mean and Standard Deviation of Pressure Shift Coefficients (in cm−1 atm−1) vs |m| Derived from Room Temperature Air-Broadening Measurements in the ν4 and ν2 Bands of 12CH4
|m|
F Species
A Species
E Species
Mean
Standard deviation
N
Mean
Standard deviation
N
Mean
Standard deviation
N
0–1.5
−0.0041
1
−0.0025
1
2–3.5
−0.0026
0.0015
6
−0.0030
0.0026
2
−0.0022
0.0005
2
4–5.5
−0.0017
0.0026
14
−0.0026
0.0015
4
−0.0031
0.0009
4
6–7.5
−0.0026
0.0035
26
−0.0025
0.0023
12
−0.0024
0.0013
7
8–9.5
−0.0022
0.0025
28
−0.0035
0.0028
10
−0.0025
0.0022
11
10–11.5
−0.0021
0.0042
27
−0.0029
0.0025
12
−0.0034
0.0025
7
12–13.5
−0.0031
0.0027
17
−0.0036
0.0030
9
−0.0032
0.0016
7
14–15.5
−0.0030
0.0038
26
−0.0026
0.0017
9
−0.0033
0.0011
8
16–17.5
−0.0031
0.0047
18
−0.0038
0.0028
7
−0.0037
0.0021
7
18–19.5
−0.0019
0.0050
6
−0.0044
0.0057
4
−0.0035
0.0013
2
N is the number of measured lines.
Table XI
Comparison of Measured and HITRAN 86 Line Positionsa
CH4 in dry air
CH4 in N2
All Lines
Mean (ν0 − νHITRAN)
0.000067 cm−1
0.000180 cm−1
Standard deviation (ν0 − νHITRAN)
0.000690 cm−1
0.000404 cm−1
Number of lines
294
103
Lines with intensities above 1.0 × 10−20 cm−1/molecule cm−2 at 296 K
Mean (ν0 − νHITRAN)
0.000134 cm−1
0.000152 cm−1
Standard deviation (ν0 − νHITRAN)
0.000277
0.000293
Number of lines
98
49
νHITRAN is the line center position (in cm−1) listed in the 1986 HITRAN line parameters compilation3 multiplied by 0.99999977 to conform to the standards of Brown and Toth.6
Tables (11)
Table I
Experimental Conditions
Gas mixture
Pressure (Torr)
Path (cm)
1.005% CH4 in dry air
200.0, 275.0, 350.0, 425.0, 550.1
5.0
50.2, 200.0, 275.5,
25.0
350.2, 425.3, 502.6, 551.0
2.58% CH4 in dry air
199.6, 275.6, 350.6, 425.0, 550.0
150.0
1.006% CH4 in N2
200.1, 275.0, 350.1, 425.1, 550.0
25.0
Pure CH4
1.10
5.0
1.01
25.0
1.01
150.0
Table II
Halfwidth and Pressure Shift Coefficientsa Measured in the ν4 Band of 12CH4
Halfwidth coefficients are in cm−1 atm−1 at 296 K. Pressure shift coefficients are in cm−1 atm−1 at about 298 K. Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
1986 HITRAN line parameters compilation3 values.
Measurements with 2 sigma uncertainties (in parentheses) are those of Malathy Devi et al.14 The other values are the N2-broadened width coefficients of Varanasi el al.13
Table III
Halfwidth and Pressure Shift Coefficientsa Measured in the ν2 Band of 12CH4
Halfwidth coefficients are in cm−1 atm−1 at 296 K. Pressure shift coefficients are in cm−1 atm−1 at about 298 K. Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
1986 HITRAN line parameters compilation3 values.
Measurements and 2 sigma uncertainties of Malathy Devi et al.15
Table IV
Comparison of Air-Broadened Halfwidth Coefficients (cm−1 atm−1 at 296 K) Measured in Both the R and P Branches of the ν4 Band
Values in parentheses are 2 sigma uncertainties in units of the last quoted digit.
Ratio of the halfwidth coefficient in the R branch to the corresponding value in the P branch.
2 sigma uncertainty in R.
Table V
Mean and Standard Deviation of the Ratio of R- branch to P- branch Air-Broadened Halfwidth Coefficients
Species
Mean
Standard deviation
N
F
0.99
0.04
45
A
0.96
0.02
16
E
1.01
0.09
19
N is the number of transitions measured in both the R and P branches.
Table VI
Mean and Standard Deviation of Halfwidth Coefficient (in cm−1 atm−1 at 296 K) vs |m| Derived from Air-Broadening Measurements in the ν4 and ν2 Bands of 12CH4
|m|
F species
A speciese
E species
Mean
Standard deviation
N
Mean
Standard deviation
N
Mean
Standard deviation
N
0–1.5
0.066
1
0.056
1
2–3.5
0.066
0.002
6
0.066
0.006
2
0.061
0.006
2
4–5.5
0.066
0.003
14
0.063
0.006
4
0.058
0.002
4
6–7.5
0.064
0.003
26
0.061
0.004
12
0.056
0.005
7
8–9.5
0.058
0.003
28
0.058
0.006
10
0.052
0.005
11
10–11.5
0.054
0.006
27
0.053
0.005
12
0.045
0.009
7
12–13.5
0.051
0.004
17
0.052
0.006
9
0.041
0.007
7
14–15.5
0.047
0.007
26
0.044
0.008
9
0.036
0.007
8
16–17.5
0.047
0.005
18
0.044
0.005
7
0.029
0.010
7
18–19.5
0.045
0.004
6
0.039
0.005
4
0.028
0.009
2
N is the number of measured lines.
Table VII
Comparison Between Air-Broadened Halfwidth Coefficients (cm−1 atm−1 at 296 K) Measured in the R Branch of the ν4 Band in this Study and the Calculated Values of Tejwani et al.25
m
Species
Measured
Calculated
Ratio
2
F1
0.0630(10)
0.0606
1.039
3
F2
0.0651(14)
0.0679
0.959
4
F1
0.0668(17)
0.0595
1.123
F2
0.0678(10)
0.0671
1.011
5
F2
0.0641(3)
0.0660
0.972
F1
0.0684(3)
0.0659
1.038
6
F2
0.0652(5)
0.0648
1.007
7
F1
0.0665(8)
0.0645
1.032
Notes: (1) Only lines resulting from a single K state are listed.
Table VIII
Mean and Standard Deviation of Halfwidth Coefficients Obtained In this Study Ratloed to Previously Reported Values
Values in parentheses are 2σ uncertainties in units of the last quoted digit.
Permitted transitions, this study
Permitted transitions from Benner et al.30 ν4 band halfwidth coefficient divided by ν3 band halfwidth coefficient.
Table X
Mean and Standard Deviation of Pressure Shift Coefficients (in cm−1 atm−1) vs |m| Derived from Room Temperature Air-Broadening Measurements in the ν4 and ν2 Bands of 12CH4
|m|
F Species
A Species
E Species
Mean
Standard deviation
N
Mean
Standard deviation
N
Mean
Standard deviation
N
0–1.5
−0.0041
1
−0.0025
1
2–3.5
−0.0026
0.0015
6
−0.0030
0.0026
2
−0.0022
0.0005
2
4–5.5
−0.0017
0.0026
14
−0.0026
0.0015
4
−0.0031
0.0009
4
6–7.5
−0.0026
0.0035
26
−0.0025
0.0023
12
−0.0024
0.0013
7
8–9.5
−0.0022
0.0025
28
−0.0035
0.0028
10
−0.0025
0.0022
11
10–11.5
−0.0021
0.0042
27
−0.0029
0.0025
12
−0.0034
0.0025
7
12–13.5
−0.0031
0.0027
17
−0.0036
0.0030
9
−0.0032
0.0016
7
14–15.5
−0.0030
0.0038
26
−0.0026
0.0017
9
−0.0033
0.0011
8
16–17.5
−0.0031
0.0047
18
−0.0038
0.0028
7
−0.0037
0.0021
7
18–19.5
−0.0019
0.0050
6
−0.0044
0.0057
4
−0.0035
0.0013
2
N is the number of measured lines.
Table XI
Comparison of Measured and HITRAN 86 Line Positionsa
CH4 in dry air
CH4 in N2
All Lines
Mean (ν0 − νHITRAN)
0.000067 cm−1
0.000180 cm−1
Standard deviation (ν0 − νHITRAN)
0.000690 cm−1
0.000404 cm−1
Number of lines
294
103
Lines with intensities above 1.0 × 10−20 cm−1/molecule cm−2 at 296 K
Mean (ν0 − νHITRAN)
0.000134 cm−1
0.000152 cm−1
Standard deviation (ν0 − νHITRAN)
0.000277
0.000293
Number of lines
98
49
νHITRAN is the line center position (in cm−1) listed in the 1986 HITRAN line parameters compilation3 multiplied by 0.99999977 to conform to the standards of Brown and Toth.6
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