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Intensities and pressure-broadened widths of CO2 R-branch lines at 15 μm from tunable laser measurements
1.Quant. Spectrosc. Radial. Transfer Vol. 24.~. 343-345 Printed inGreat Britain Per&mm Press Ltd., 1980.
NOTE INTENSITIES AND PRESSURE-BROADENED WIDTHS OF CO, R-BRANCH LINES AT 15 pm FROM TUNABLE LASER MEASUREMENTS L. TETTEMER and WALTER G. PLANET
GREGORY National Oceanic and Atmospheric
Administration, National Environmental DC 20233, U.S.A.
Satellite Service, Washington,
(Received 14 March 1980) Abstract-Intensities and half-widths of individual lines, over the temperature range 200-325°K in the 15 pm bands of ‘V602. have been determined with a tunable diode laser spectrometer. Measurements were made on pure CO2 and on dilute CO*-in-N2 mixtures on the R-branches of the Ol’O-OO”O and O2%-Ol’O transitions. Intensities are approximately equal to those listed in the AFCL compilation. The pressurebroadened half-widths follow the general relationship bLo(T) = bLotTo) [To/T]” where n varies considerably from line to line but is always greater than f.
RESULTS Intensities and half-widths of several lines in the R-branches of the 01’~OO“0and 0220-01’0 transitions of 12C”j02have been measured. The measurements were made with the tunable diode laser spectrometer using techniques previously discussed in Refs. 1 and 2. Intensities, S(300), were measured on natural CO2 of 99.8% purity at low pressures (5-100 x 10m3torr) in a 1 m cell at 300°K. Intensities of these lines were determined using the Rodgers and Williams3 relationship between equivalent width and intensity of Doppler lines. The results are shown in Table 1. Half-widths were measured on dilute mixtures of natural CO2 in N2 at a total pressure of 10 torr in a 1 m sample cell at about 25°K intervals over the temperature range 200-325°K. We assume that the broadening coefficients, 6Lo(T), determined from the measured half-widths, display a temperature dependence denoted by bLo(T) = bto(300) (300/T)“, where T is the temperature, bLo(300) is the reference broadening coefficient, and n is the temperature coefficient. Values of bLo(300)and n, computed by a least squares fit to the measurements, are shown in Table 2. Table I. Intensities, S.[cm~2atm-‘], of the IS-pm COz R-branch Doppler lines at PT = 5.0-100.0 (20.2)~ IO-‘torr, I= 100.0(+O.l) cm, and T = 299.0-301.0 (kO.l)K. The standard deviations are given in parentheses. OllO-00’0 J
Transition
0220-0110 Transition
s
J
S
PO
3.60 C.141
19
22
3.51 (.3O)
21
3.162
24
3.28 C.12)
23
0.144 C.003)
28
2.L2 C.20)
24
0.139 c.0051
30
2.16 C.30)
27
0.110 (.ooRl
32
1.99 C.20)
30
0.101 (.OOS)
3h
1.55 C.14)
35
0.0615 C.0029)
36
1.25 C.08)
36
0.0545
38
1.09 C.07)
&O
0.757 (.Oh7)
44
0.469 C.021)
46
0.357 C.011)
50
0.'186c.007)
343
0.170 (.006) C.021)
t.00141
344
G. L. TET~EMER and W. G. PI.ANET Table
2. Reference broadening coefficients, adened, IS-pm COz R-branch
b,“(300) [cm-‘atm-‘1, and temperature coefficients, lines. The standard deviations are given in parentheses.
OllO-00'0 Transition J
02zO-0110 Transition n
b$300)
J
b;(3OO!
I.
20
.070(.005)
0.865(.024)
19
.075(.008)
24
.072(.013)
1.003(.057)
27
.068(.008)
0.73lC.055)
20
.080(.010)
0.608(.048)
30
.068(.009!
0.799(.055)
0.635(.048)
30
.079(.006)
0.661c.027)
35
.067(.004!
1.296c.061)
32
078(.005!
0.673(.022)
36
.068(.008)
l.Z78(.lhZ)
40
.064(.008)
0.7531.037)
44
.068(.010)
0.969c.045)
46
059c.012)
0.955(.054)
.062(.012)
50
n, of Nz-bro-
1.132’(.058)
A major purpose of these measurements is to obtain the most accurate values for the spectroscopic parameters to be used in calculating transmittances through real atmospheres. While it is not practical to make measurements on all of the lines in a spectral region or observation band-pass, it is reasonable to investigate selected lines in order to construct a model of the parameters for all the lines within the bandpass. These model parameters, derived Table
3. Spectral
model
parameters
of the
IS-pm
CO2
R-branch
lines;
(a) OI’O-WO
transition
(a)
transition,
(b) 02%01’0
(b)
T
J
-1 “,Cill
S(300)
b;(300)
J
n
-
-1 v,cm
s(300)
~$300:
”
20
683.9583
3.76'
0.077
0.852
19
683.ao45 0.172'
0.074
0.948
22
605.5552
3.53'
0.076
0.852
20
684.3671 0.167
0.073
0.948
24
687.1552
3.21"
0.075
0.852
21
685.4541 0.161'
0.073
0.948
26
688.7581
2.85
0.074
0.852
22
685.968c 0.154
0.072
0.948
28
690.3640
2.53s
0.073
0.852
23
687.111: 0.147*
0.072
0.948
30
691.9728
2.14"
0.072
0.852
24
687.571: 0.139*
0.071
0.44a
32
693.5844
1.80s
0.071
0.852
25
600.7771 0.132
0.371
0.948
3h
695.1989
1.49*
0.070
0.852
26
689.177' 0.124
0.071
0.948
36
696.0162
1.20*
0.069
0.852
27
690.450: 0.116'
0.070
0.948
38
698.4362
0.96'
0.068
0.852
28
690.78hl 0.10A
0.070
0.948
40
700.0590
0.76
0.067
0.852
29
692.1301 0.100
0.069
0.948
42
701.6045
0.58
0.066
0.852
30
692.3981 3.091*
0.069
0.948
44
703.3126
0.44*
0.065
0.852
31
693.819: 0.084
0.06?
0.948
46
704.9433
0.33*
0.064
0.852
32
694.0:31 0.077
0.068
0.948
48
706.5765
0.24
0.063
0.852
31
695.515: 0.070
0.068
0.948
50
708.2123
0.19*
0.062
0.85"
34
695.63Of o.064
O.Oh?
0.948
35
697.218( 0.053"
0.06;
0.948
36
697.2501 0.051"
0.066
n.9;9
38
698.8731 n.ci41
0.066
0.34e
37
698.929' L.O.,/,
o.066
0 94a
40
700.4994 1.032
1.065
q.949
39
700.6483 3.036
1.065
3.$48
47
702.1277 0.024
3.06L
1.348
41
702.3742 0.02a
3.064
?.94H
li
703.7587 0.018
7.363
, .9’4R
43
704.1073 D.02i
1.064
I.94R
46
705.7921 0.014
3.062
1.948
15
705.8477 0.016
>.oG?
3.94l!
48
707.0281 0.010
0.061
3.918
47 __
'707.5952 O.Ol?
3.067
3.9148
_
‘Note:
measurements made on these lines
-
Intensities and pressure-broadened widths of CO2 R-branch lines
345
from a fit to measured values, can then be used to calculate transmittances. The parameters we modeled were S(300), bLo(300),and n for the 01’0-00 ‘0 and 0220-01’0 transitions from 683.8 to 708.2cm-‘. The parameters are listed in Table 3. The positions of the lines, V, are from Drayson. We modeled the intensities S(300), assuming the temperature dependence and J-dependence of line intensities as listed on the AFGL tape’ to be correct. A least-squares fit was performed on the intensities and compared to those listed on the AFGL tape, SAFGL.We found, for the Ol’(MooOtransition the value S = 0.99 SAFoLand, for the 0220-01’0 transition, S = 0.98 S,,,. We modeled the reference broadening coefficients, bLo(300),assuming the J-dependence to be linear and fit a least-squares line to the measurements. We modeled the temperature coefficient, assuming it to be constant. Although n varies from line to line, we could not discern any meaningful J-dependence. For the 01’0-00”0 transition, n = 0.852; for the 0220-01i0 transition, n = 0.948.
I. 2. 3. 4. 5.
REFERENCES W. G. Planet, G. L. Tettemer, and J. S. Knoll, JQSRT 20, 547 (1978). W. G. Planet and G. L. Tettemer, JQSRT 22, 345 (1979). C. D. Rodgers and A. P. Williams, JQSRT 14,319 (1974). S. R. Drayson, Unpublished data. L. S. Rothman and R. A. McClatchey, Appl. Opt. 15,2616 (1976).
NOTE INTENSITIES AND PRESSURE-BROADENED WIDTHS OF CO, R-BRANCH LINES AT 15 pm FROM TUNABLE LASER MEASUREMENTS L. TETTEMER and WALTER G. PLANET
GREGORY National Oceanic and Atmospheric
Administration, National Environmental DC 20233, U.S.A.
Satellite Service, Washington,
(Received 14 March 1980) Abstract-Intensities and half-widths of individual lines, over the temperature range 200-325°K in the 15 pm bands of ‘V602. have been determined with a tunable diode laser spectrometer. Measurements were made on pure CO2 and on dilute CO*-in-N2 mixtures on the R-branches of the Ol’O-OO”O and O2%-Ol’O transitions. Intensities are approximately equal to those listed in the AFCL compilation. The pressurebroadened half-widths follow the general relationship bLo(T) = bLotTo) [To/T]” where n varies considerably from line to line but is always greater than f.
RESULTS Intensities and half-widths of several lines in the R-branches of the 01’~OO“0and 0220-01’0 transitions of 12C”j02have been measured. The measurements were made with the tunable diode laser spectrometer using techniques previously discussed in Refs. 1 and 2. Intensities, S(300), were measured on natural CO2 of 99.8% purity at low pressures (5-100 x 10m3torr) in a 1 m cell at 300°K. Intensities of these lines were determined using the Rodgers and Williams3 relationship between equivalent width and intensity of Doppler lines. The results are shown in Table 1. Half-widths were measured on dilute mixtures of natural CO2 in N2 at a total pressure of 10 torr in a 1 m sample cell at about 25°K intervals over the temperature range 200-325°K. We assume that the broadening coefficients, 6Lo(T), determined from the measured half-widths, display a temperature dependence denoted by bLo(T) = bto(300) (300/T)“, where T is the temperature, bLo(300) is the reference broadening coefficient, and n is the temperature coefficient. Values of bLo(300)and n, computed by a least squares fit to the measurements, are shown in Table 2. Table I. Intensities, S.[cm~2atm-‘], of the IS-pm COz R-branch Doppler lines at PT = 5.0-100.0 (20.2)~ IO-‘torr, I= 100.0(+O.l) cm, and T = 299.0-301.0 (kO.l)K. The standard deviations are given in parentheses. OllO-00’0 J
Transition
0220-0110 Transition
s
J
S
PO
3.60 C.141
19
22
3.51 (.3O)
21
3.162
24
3.28 C.12)
23
0.144 C.003)
28
2.L2 C.20)
24
0.139 c.0051
30
2.16 C.30)
27
0.110 (.ooRl
32
1.99 C.20)
30
0.101 (.OOS)
3h
1.55 C.14)
35
0.0615 C.0029)
36
1.25 C.08)
36
0.0545
38
1.09 C.07)
&O
0.757 (.Oh7)
44
0.469 C.021)
46
0.357 C.011)
50
0.'186c.007)
343
0.170 (.006) C.021)
t.00141
344
G. L. TET~EMER and W. G. PI.ANET Table
2. Reference broadening coefficients, adened, IS-pm COz R-branch
b,“(300) [cm-‘atm-‘1, and temperature coefficients, lines. The standard deviations are given in parentheses.
OllO-00'0 Transition J
02zO-0110 Transition n
b$300)
J
b;(3OO!
I.
20
.070(.005)
0.865(.024)
19
.075(.008)
24
.072(.013)
1.003(.057)
27
.068(.008)
0.73lC.055)
20
.080(.010)
0.608(.048)
30
.068(.009!
0.799(.055)
0.635(.048)
30
.079(.006)
0.661c.027)
35
.067(.004!
1.296c.061)
32
078(.005!
0.673(.022)
36
.068(.008)
l.Z78(.lhZ)
40
.064(.008)
0.7531.037)
44
.068(.010)
0.969c.045)
46
059c.012)
0.955(.054)
.062(.012)
50
n, of Nz-bro-
1.132’(.058)
A major purpose of these measurements is to obtain the most accurate values for the spectroscopic parameters to be used in calculating transmittances through real atmospheres. While it is not practical to make measurements on all of the lines in a spectral region or observation band-pass, it is reasonable to investigate selected lines in order to construct a model of the parameters for all the lines within the bandpass. These model parameters, derived Table
3. Spectral
model
parameters
of the
IS-pm
CO2
R-branch
lines;
(a) OI’O-WO
transition
(a)
transition,
(b) 02%01’0
(b)
T
J
-1 “,Cill
S(300)
b;(300)
J
n
-
-1 v,cm
s(300)
~$300:
”
20
683.9583
3.76'
0.077
0.852
19
683.ao45 0.172'
0.074
0.948
22
605.5552
3.53'
0.076
0.852
20
684.3671 0.167
0.073
0.948
24
687.1552
3.21"
0.075
0.852
21
685.4541 0.161'
0.073
0.948
26
688.7581
2.85
0.074
0.852
22
685.968c 0.154
0.072
0.948
28
690.3640
2.53s
0.073
0.852
23
687.111: 0.147*
0.072
0.948
30
691.9728
2.14"
0.072
0.852
24
687.571: 0.139*
0.071
0.44a
32
693.5844
1.80s
0.071
0.852
25
600.7771 0.132
0.371
0.948
3h
695.1989
1.49*
0.070
0.852
26
689.177' 0.124
0.071
0.948
36
696.0162
1.20*
0.069
0.852
27
690.450: 0.116'
0.070
0.948
38
698.4362
0.96'
0.068
0.852
28
690.78hl 0.10A
0.070
0.948
40
700.0590
0.76
0.067
0.852
29
692.1301 0.100
0.069
0.948
42
701.6045
0.58
0.066
0.852
30
692.3981 3.091*
0.069
0.948
44
703.3126
0.44*
0.065
0.852
31
693.819: 0.084
0.06?
0.948
46
704.9433
0.33*
0.064
0.852
32
694.0:31 0.077
0.068
0.948
48
706.5765
0.24
0.063
0.852
31
695.515: 0.070
0.068
0.948
50
708.2123
0.19*
0.062
0.85"
34
695.63Of o.064
O.Oh?
0.948
35
697.218( 0.053"
0.06;
0.948
36
697.2501 0.051"
0.066
n.9;9
38
698.8731 n.ci41
0.066
0.34e
37
698.929' L.O.,/,
o.066
0 94a
40
700.4994 1.032
1.065
q.949
39
700.6483 3.036
1.065
3.$48
47
702.1277 0.024
3.06L
1.348
41
702.3742 0.02a
3.064
?.94H
li
703.7587 0.018
7.363
, .9’4R
43
704.1073 D.02i
1.064
I.94R
46
705.7921 0.014
3.062
1.948
15
705.8477 0.016
>.oG?
3.94l!
48
707.0281 0.010
0.061
3.918
47 __
'707.5952 O.Ol?
3.067
3.9148
_
‘Note:
measurements made on these lines
-
Intensities and pressure-broadened widths of CO2 R-branch lines
345
from a fit to measured values, can then be used to calculate transmittances. The parameters we modeled were S(300), bLo(300),and n for the 01’0-00 ‘0 and 0220-01’0 transitions from 683.8 to 708.2cm-‘. The parameters are listed in Table 3. The positions of the lines, V, are from Drayson. We modeled the intensities S(300), assuming the temperature dependence and J-dependence of line intensities as listed on the AFGL tape’ to be correct. A least-squares fit was performed on the intensities and compared to those listed on the AFGL tape, SAFGL.We found, for the Ol’(MooOtransition the value S = 0.99 SAFoLand, for the 0220-01’0 transition, S = 0.98 S,,,. We modeled the reference broadening coefficients, bLo(300),assuming the J-dependence to be linear and fit a least-squares line to the measurements. We modeled the temperature coefficient, assuming it to be constant. Although n varies from line to line, we could not discern any meaningful J-dependence. For the 01’0-00”0 transition, n = 0.852; for the 0220-01i0 transition, n = 0.948.
I. 2. 3. 4. 5.
REFERENCES W. G. Planet, G. L. Tettemer, and J. S. Knoll, JQSRT 20, 547 (1978). W. G. Planet and G. L. Tettemer, JQSRT 22, 345 (1979). C. D. Rodgers and A. P. Williams, JQSRT 14,319 (1974). S. R. Drayson, Unpublished data. L. S. Rothman and R. A. McClatchey, Appl. Opt. 15,2616 (1976).