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Aeronomic problems of molecular oxygen photodissociation—II. Theoretical absorption cross-sections of the Schumann-Runge bands at 79 K
PImet. Spa Sri.. Vol. 34. No. 10. pp. 1039-1058.1988 Printed in Great Britain.
W32-0433/88 53.W+O.O0 Pngamon Pros pk
AERONOMIC PROBLEMS OF MOLECULAR OXYGEN PHOTODISSOCIATION-II. THEORETICAL ABSORPTION CROSS-SECTIONS OF THE SCHUMANN-RUNGE BANDS AT 79 K MARCEL NKOLET,* STANISLAS-IJRt amdROBERT RRNNES Institut d’Mronomie Spatiale de Belgique, 3 Avenue Circulaire, B-l 180 Brussels, Belgium (Received 22 April 1988) Alrstraet-Theoretical spectra corresponding to the domain of the rotation lines of the 2-O to 12-4 bands of the B%;-X%; Schumann-Runge system of O2 at 79 K are presented in graphical format. Calculated absorption cross-sections are compared with recent laboratory measurements made at the same temperature. The calculations were based on previous theoretical detonations at 300 K established after a comparison with results of laboratory measurements made at the same temperature. Such an analysis in which the band oscillator strengths are associated with averaged linewidtbs of the rotation lines for each band and with their underlying continuum, gives consistent values for the various spectroscopic parameters
of the O2 !Mnunann-Runge bands.
1. ~RO~U~ON
In a recent publication (Nicolet et al., 1987),a theoretical determination of the rotational structure and absorption cross-sections of the O2 Schumann-Runge bands (see Table 1) was made at 300 K. This detailed analysis was based on the experimental results obtained by the Hazard-S~thso~an Group on the photodissociation absorption cross-sections at high resolution in the spectral region corresponding to the u’ = 1-12 bands (Yoshino et al., 1983). After the first detailed analyses such as the wavelength assignments, for u’ 2 12, of Brix and Herzberg (1954) and, for u’ < 13, of Ackerman and BiaumC (1970) and Biaume (1972), extensive wavenumber measurements of the rotation lines of the O2 Schumann-Runge absorption bands were provided by Yoshino er al. (1984). These sets of data are also the most accurate and most complete since the crosssections are absolute, the line~dths being in excess of the instrument resolution for the various bands studied. Recent rotational constants (Table 2) of the upper electronic state of the Schumann-Runge system have also been published by Cheung et al. (1986). These *Also with: Communications and Space Sciences Laboratory, Penn State University, University Park, PA 16802, U.S.A. t Now at : Commission of the European Communities, ISPRA Establishment, Italy, Chemistry Division, Air Pollution Sector.
constants make it possible to calculate the wavenumbers of the rotation lines. The same spectroscopic constants have been also determined by Lewis et al. (1986a,b) from the wavenumber measurements of Yoshino et al. (1984). The adopted band oscillator strengths of the (u’, 0) and (v’, 1) bands were based on the various results of Yoshino et al. (1983), of Cheung er ai. (1986), and of Lewis er al. (1986a). The mean predissociation linewidths were determined after a detailed comparison between calculated absorption cross-sections and the experimental results pub~shed by Yoshino et al. (1983) in the spectral region corresponding to the U’ = 1-12 bands. However, the absorption cross-sections throughout this region may depend also on the underlying continuum corresponding near 50,000 cm-’ to the O2 Herzberg continuum (see Nicolet and Kennes, 1986, 1988a). At wavenumbers greater than 55,000 cm-’ , the OZ Schumann-Runge wntinuum (see Lewis er al., 198Sa,b) plays a role related to the temperature. The recent extensive determination by Yoshino et al. (1987) of the experimental structure of the 2-O to 12-O bands at 79 K provides a direct test for the theoretical determination which must be used for aeronomic purposes (tem~rat~es generally between 170 and 270 K). In the present paper experimentai data and theoretical results at 79 K are compared to provide an improved understanding of the absorption structure in the predissociation region of the O2 Schumann-Runge system.
1039
1040
M.
NICOLET
et al.
TABLE 1. ADOPTED SPECTRALINTERVALSFOR THE SCHUMANN-RUNGE BANDS OF O2
Band
Wawnuabw
(cm-')
Wav*lsngth
Mean
(rim)
M*an
Ai
49000-49500
49250
500
204.08-202.02
203.04
2.06
I-O
49500-50050
49777
550
202.02-199.80
200.90
2.22
2-o
50050-50715
50382
665
199.80-197.18
19a.48
2.62
3-0
50715-53355
51035
640
197.18-194.72
195.94
2.46
4-O
51355-51975
51665
620
194.72-192.40
193.55
2.32
5-O
51975-52565
52270
590
192.40-190.24
191.31
2.16
6-O
52565-53130
52847
565
190.24-188.22
189.22
2.02
188.22-186.36
187.28
1.86
o-o
7-o
53130-53660
53395
530
8-O
53660-54160
53910
500
186.36-184.64
185.49
1.72
9-O
54160-54625
54392
465
184.64-183.07
183.85
1.57
to-o
54625-55055
54840
430
183.07-181.64
182.35
1.43
II-O
55055-55440
55247
385
181.64-180.37
181.00
1.27
179.80
1.13
12-o
55440-55790
55615
350
180.37-179.14
13-o
55790-56090
55940
300
179.24-178.28
178.76
0.96
14-o
56090-56345
56217
255
178.28-177.48
177.88
0.80
15-O
56345-56550
564Jk7
205
177.4a-176.83
177.16
0.65
16-0
56550-56725
56637
175
176.83-176.29
176.56
0.57
17-o
56725-56855
56790
130
176.29-175.89
176.09
0.40
175.72
0.33
775.45
0.23
18-0
56855-56960
56907
105
?75.89-175.56
19-O
56960-57035
56997
75
175.56-175.33
2. THE BAND OSCILLATOR
STRENGTHS
The Schumann-Runge bands, analyzed many times, have generated several determinations of their mean oscillator strengths. The values adopted here (Table 3) are based mainly on the recent results of the Cambridge and Canberra groups to generate a consistent set of data (Yoshino et ul., 1983 ; Cheung eta& 1984;Yosbinoetaf., 1987; Lewisetal., 1986a,b) and also on the analysis of Allison et al. (1971). Since it is practically impossible to introduce an exact oscillator strength adapted to all circumstances, mean values have been adopted for each vibrational level. The uncertainties should be generally less than 5% but could reach perhaps 5-10% for two or three bands. In any case, the values given in Table 3 must be considered as averaged band oscillator strengths to be adopted in order to determine the effective linewidths of the rotational lines of bands corresponding to the various vibrational levels from U’ = 0 to v’ = 19.
The measured high resolution absorption crosssections of the Schumann-Runge bands by Yoshino et al. (1983) between 201 and 179 mn have been adopted to determine the effective rotational linewidths. Even when experimental results exhibited systematic variations with rotational levels (Lewis et al., 1986a,b), an equivalent band linewidth was adjusted to fit the experimental absolute cross-sections after the introduction of the effect of an underlying continuum. The He&erg continuum plays an important role in the determination of the absorption cross-sections of the first Schumann-Runge bands. The SchumannRunge continuum is subject to a variation related to the population of the rotational and vibrational levels in the spectral range of the last bands near the normal continuum limit. The best-fit model calculated values of the O2 absorption cross-sections with the experimental
Aeronomic problems of oxygen photodissociationTABLE2.
hOPTED
1041
SPECTROSZOPIC CONSTANTS FOR THE UPPER STATE OF THE %XUMANNRUNGEBANDSOF 0,m COMPUTELINEPOSITIONS
Band
vo(cm-‘)
B ”
o-o
49357.96
0.8132
D ”
x
4.50 x 1O-6
”
1.69
y,
- 2.80.~.10-~
1-o
50045.53
0.7993
4.20
1 .70
- 2.60
2-O
50710.68
0.7860
5.80
1.69
- 2.90
3-O
51351 .94
0.7705
5.20
1.70
- 2.60
4-o
51969.36
0.7550
5.97
1.81
- 3.00
5-o
52560.94
0.7377
5.80
1.75
- 2.20 - 2.10
6-0
53122.65
0.7187
5.00
1.79
7-o
53655.95
0.7010
8.60
1.82
- 2.10
8-0
54156.22
0.6770
6.70
1.91
- 2.30
9-O
54622.50
0.6514
6.30
2.04
- 2.10
10-O
55051.16
0.6263
9.90
2.10
- 4.10
11-O
55439.23
0.5956
9.40
2.17
- 3.80
12-o
55784.58
0.5626
1.37 x 1O-5
2.37
- 5.40
13-o
56085.44
0.5242
1.63
2.51
- 8.40
14-o
56340.42
0.4832
2.09
2.81
- 1.16 x lo-'
15-o
56550.62
0.4391
2.54
3.30
- 1.64
16-0
56719.62
0.3934
3.08
4.11
- 2.41
17-O
56852.45
0.3457
3.34
5.18
- 3.48
18-O
56951.60
0.2872
5.50
6.51
- 4.94
19-o
57025.80
0.2649
6.00
7.63
- 6.04
- band origin = T + $AY as given by Cheung et al. “0 constants for vibrational 1~~1s Bv and DV - rotational
xv and Yv splitting For 18-O and 19-0,
constants see
Fang,
for
levels.
Wofsy and Dalgarno
have been used to determine the rotational linewidths adapted to each band. The adopted mean rotational linewidths are given in Table 4. The computation was made at each 0.1 cm-’ with a contributing spectral range of 500 cm-’ for a Voigt profile. Since realistic high resolution synthetic spectra require line centers to be located to within about 0.1 cm-‘, the wavenumbers obtained at each 0.1 cm-’ between 49,000 and 57,000 cn-’ give the possibility of determining the detailed structure of the whole spectrum and of studying the effect of temperature. In addition, the relative role of the underlying con-
measurements
vibrational
(19%)
(1974).
tinua with their related accuracy can be investigated
as a function of temperature and wavelength. 4. THE O2 HERZBRRG
CONTINUUM
The absorption cross-sections of the O2 Herzberg continuum at wavelengths greater than 200 nm used before 1980 must now be replaced by experimental and observational results obtained recently (1984-1986). An analysis made by Nicolet and Kennes (1986, 1988) leads to the adoption of an empirical formula for the absorption cross-section,
M. NICOLETet al.
1042
TABLE3. f&PTFD MEAN ABWRPTIONGK!ULATORSTRENGTIS j&,, FORTHEs CHUMANN-RUNGEBANDS OF o2 DEDUCED FROM ABSORPTION
fw
Vf
0 1
$.;;
2 3 4 5 6 7 8
1.9 x 8.2 x 2.7 x 7.4 x 1.6 x 3.4 x 6.2 x 1.0 x 1.5 x 1.9 x 2.4 x 2.7 x 2.8 x 2.7 x 2.6 x 2.2 x 1.7 x 1.3 x
1; II 12 13 14 15 16 :i 19
SPECTRA
w;
7.6 x lo-9
lo-* lo-8 1O-7 lo-7 lo+ 1o-6 IO-’ lo+ 10-j lo-5 IO-’ IO-’ l0-5 lO-5 lO-5 lo-’ lo-J Io-5
8.2 x 4.6 x 1.8 x 5.0 x 1.3 x 2.7 x 5.0 x 8.6 x 1.2 x 1.7 x 2.1 x 2.6 x 2.6 x 2.9 x 2.7 x 2.0 x 1.6 x 1.3 x 1.6 x
cTHER(OZ)= 7.5 x lo-2yv/5 x
l-id lo-* lo-’ lO-6 lo-6 lo-s IO-’ lo-5 lo-5 lo-4 lo-4 lo-4 IO-4 lO-4 lo-‘+ lo-“ lo-4 lO-4 lo-4 lO-4
x 104)
are given for spectral intervals of 500 cm-‘, mean absorption cross-sections of the O2 Herzberg continuum are used in our computations. The adopted numerical values are given in Table 5. 5. ANALYSIS
OF THE PHOTOABSORPTION CROSS-SECTIONS
In our general analysis (Nicolet et al., 1987), the line positions and rotational assignments are reproduced for intervals of 250 cm-’ and the theoretical and experimental absorption cross-sections are presented graphically (1 cm-’ per mm) at 300 K throughout the 49,000-57,000 cm-’ wavenumber region corresponding to all bands with u’ = O-19 and v” = 0 and I. This graphical comparison between the calculated and measured absorption cross-sections begins at 49,750 cm-‘, 1-O and 3-l bands, and ends at 55,800 cm-‘, 12-O and 19-1 bands. In order to show the principal features of the spectrum, three different regions (rotational lines with their identifications in Tables 6,7 and 8) are illustrated in various figures by a ~~-lo~~t~c plot of the absorption cross-sections, namely between 50,500 and 50,750 cm-’ (Fig. la), 51,750 and 52,000 cn-’ {Fig. Za), and 54,000 and 54,250 cm-’ (Fig. 3a). Such
exp { -5O[in (v/(5x 104)12)cm-‘.
Although the available sets of Herzberg continuum cross-sections derived from laboratory measurements seem to reach an acceptable agreement with their experimental accuracy at wavelengths greater than 200 nm, the errors of the experimental or theoretical determinations prevent an exact extrapolation for the Herz&rg con~nu~ underlying the SchumannRunge bands between 190 and 200 nm. Nevertheless, the stratospheric determinations are not in disagreement with the values deduced from the formula that we have adopted. Since our final determinations of the oxygen transmittance and of the photodissociation rate constants
TABLE 4. ADGPTED MEAN ROTATIONLI~~DTHS ~-RAGE BANDSOF O2 0’
cm-’
d
0
8 0:6 1.8 3.6 2.0 :*t 2:1 1.2
Cross-sections
(cm-‘)
(cm3
Interval (cm-‘)
Cross-section (cm3
49,~9,~
7.2 x lo-=
52,000-52,500
7.2 x lo-=
50,00(t50,500 49,500-50,000 50,50~51,000 51,00&51,500 51,50&52,000
7.5 7.4 7.5 7.5 7.4
53,000-53,500 52,500-53,000 53,500-54,000 54,000-54,500 54,500-55,000
E 6:4 6.0 5.6
cm-’
10 11 12
1.0 1.4 0.8
13 14 15 16 17 18 19
0.5 0.5 0.5 0.5 0.5 0.3 0.3
TABLE 5. MEAN ABSDRPTION CROSS-SECTIONS OF THE O* HERZBERG~~NTIN~~M DEDUCEDFROMFDRMULA (1) kIteNd
FOR THE
r
CROSS-SECTION -_-
----
II
2-O BAND
300
1 e4m2
;
cni’) ~
----0
7
:
CONTINUUM-;7.53x (50500
1043
-
-___
LiBORATORY 50550
K
-
j
CALCU .ATION
-
50600
WRVENUMEER
51
50
51
JO
51
FIG. I(a).T~~TI~AL.ANDE~~ERI~TALAB~~BPTI~N CROSS-SECTIONSOFTHE ~-OSCHUMANP-RUNGE BAND OF o2 BETWEZN 50,500 AND 50,750 cm-’ AT 300 K. Oscillatorstrength and linewidth are 1.9 x 1Omsand 0.6 cm-‘, respectively. Strong effect of the Herzbcrg
continuum.
-24 1 50500
300
K
50550
50500
WAVENUMBER
‘C6”
50700
FIG. l(b). ABSORPTION STRUCTUREOF THE 2-O BAND WITHVARIATIONSOF f 10 AND k20% CROSS-SECTIONOFTHEUNDERLYINGCONTTNUUM AT 300 K.
50750
IN THE
‘0
FIG.
l(c). AEWRPTION
WITH ANDWITHOUTCONTINIJIJMBET~EEN SO,~OOAND 50,750m-' AT 270 K. Differences of a factor of IO between lines at 50,500 cm-‘. STRUCTURE
FIG. I(d). ALISORPTIONSTRUCTIJRE~IITHAND~ITIIOUTCONTIN~LMBET~EEN
50,500 AND 50,750cm 'AT 190 K. Increase of differences at high rotation levels; cross-sections reaching 3 x 1O-25cm* near 50,500 cn-‘.
CROSS-SECTION
4-O BAND P15 R17
:
:
P13 R15
PllR13
P7R9
P9Rll
P5Rj
P3R5
!A ~ R17 P15
Rl9
Pl7
:j
7-l
BAND
b.S.-3d5 L.w.-1.9cfd
----
: LABORAl ‘ORY
-
’ CALCULA TION
CONTlNUUM=f -23 51750
300 K
51800
5,850
(51750 WAVENUMBER
.40x l&4cm2
cd)
51900
FIG.~(~).THEORETICALANDEXPERIMENTALABSORPTIONCROSS-SECTIONSOFTHE~SCHUMANN-RUNGE BANDOF02BETWEEN 51,750 AND 52,000Cm-'AT 300K. Oscillator strength and linewidth are 2.7 x lo-’ and 3.6 cm-‘, respectively. Linewidths of 24 compared.
~~O-270-230-,905’~oo
51830
WRVENUWBER
51900
5,950
to be
5
FIG.2(b). TEMPERATUREEFFECTONTHEROTATIONALSTRUCT~REBETWEEN 51,750 AND 52,OOOcm-‘. Effects of a temperature decrease from 300 to 270,230 and 190 K on the 4-O and 7-l bands.
IO0
1046
CROSS-SECTION
-YE
-----
-
tA30RiT0~~
8-O BAND P13
/
’ CALCULATIOI I
:
Rl3Pl1,
RllP9
“”
R7Ps
I
13 Rl
is
r
9-O BAND R23
-19
P2l
II II
IP15
-21
k!
8-O BAND
O.Sd3.2~
16O
L.W.-2.lcni’ CONTIiJUUM-6.22x (54000 5qnon
300
K
FIG.3(a).THEORETICAL
2- 1 BAND
16*4cm2
AND
5cllUO EXPERIMENTAL
WAVENUMBER
51150
CROSS-SECTIONS OF THE 8-O SC--RUNGB 54.000AND 54.250cm-’ AT 300K.
ABSORPTION
BANDOFo,BlXlWBBN
!
t 54050 ~-270-230-190 K
1ti4
L.dV.-0.8cm’
cfli’)
54050
0.$.-2.8x
541ou
UAVENUtlBER
54150
54200
5
FIG.~(~).TMPBBATUICEEPPECTONTHEROTATIONALSTNJ~TUREBETWBBN 54,000A~~ 54,250~~'. Effects of a temperature decrease from 300 to 270,230 and 190 K particularly on the lines of the 12-1 and
13-l bands.
Aeronomic problems of oxygen photodissociationfigures (Figs 1a, 2a and
3a) make it possible to perform a detailed comparison at 300 K between the calculated and measured cross-sections. The calculations also make it possible to determine the respective role of the lines and of the continuum in the O2 absorption cross-section (Fig. lb) where variations of + 10 and f20% in the underlying continuum are depicted. Other figures have been published for temperature between 270 and 190 K (examples, Figs lc and Id) in order to define for each spectral interval the exact role
of the underlying continuum at varying temperatures adopted to atmospheric conditions. Finally, Figs 2b and 2c illustrate the variations in the structure of the absorption spectrum from the laboratory temperature 300 K to atmospheric temperatures 270,230 and 190 K. It is easy to follow, with decreasing temperature, the marked variations in the absorption of the rotation lines starting from the vibrational level u” = 1. The spectral interval 50,500-50,750 cm-’ (Table 6
TABLE 6. IDENTIFICA~ON OF O2 SHUMANN-RUNGE 50750 cm-’
5*:40 50522.3 50523. 50523.6 50527.4 50527. 50528.5 50530. 50530. 50531.3 50533.2 5053s. 50540. 50550 50571. 50571. 50572. 50573.2 50573. 50580. 50593. 50533. 50533.6 50597.2 50597.5 50538.2 50600 50607. 50607. 50607.3 50613.9 50614. 50614. 50637.3 50638. 50638. 50643. 50643.5 50644. 50650 50657. 50657.6 50658. 50661.6 50661.8 50662.5 50663.2
0
7 7 7
3 1 7 7 2 3 0 0 1
4 4
A
band
1973. 30 1373.29 1973.27 1373. 13 1979. 11 1373. 08 1978.33 1978.97 1378. 66 1378.66 1378. 63
5-l 5-l 5-l 5-l 5-l 5-l 2-O 2-O 2-O 2-O 2-O 2-O
P25 P25 P25 R27 R27 R27 P15 P15 P15 R17 R17 R17
1377.39 1977.39 1977.37 1977.10 1377. 1977. 1376. 1376. 1376.53 1376.39 1976. 1376.
2-o 2-o 2-o 2-O 2-O 2-O 5-l 5-l 5-l 5-l 5-l 5-1
P13 P13 P13 Rl!i R15 R15 P23 P23 P23 R25 R25 R25
2-O 2-o 2-o 2-O 2-O 2-O 2-O 2-o 2-o 2-O 2-O 2-O
Pll PI1 Pll R13 R13 R13 P 9 P 3 P 3 RI1 RI1 RI 1
5-1 5-l 5-l 5-l 5-l 5-l 2-O
P21 P21 P21 R23 R23 R23 P 7
1378.33
OS 07 56 55
38 35
1376.00 1975.99 1375.38 1375. 74
0 6 0 4 4 1
1975. 74 1975. 71 1374.81 1374.80 1974. 73 1374.53 1374.53 1974.57
6
1974. 04 1374.04
1
1374.02
1373. 88 1373.87 1373. 85 1973.82
1047
ROTATIONAL
50663.3 50663.6 50667. 50667. 50668.3 50683. 50683. 50683. 50686.8 50686. 50687. 50698. 50698. 50698.6 50700 50700.6 50700.6 50701. 50707.9 50703. 5070s. 50703. 50710.3 50712. 50712. 50716. 50716. 50717.2 50720. 50720.6 50721.2 50726. 50727. 50727.
band
A
”
7 7 3 4 7 8 3 1 3
1 1 3 7 5 6 7 7 4
3 I 3
1973. 1373.80 1373.64 1973.64 1373. 1373.04 1373. 1373.02 1972. 1372. 1972.88 1972. 1372. 1372. 1972.37 1972.36 1372.35 1372. 1972. 1372. 1972. 1971.36 1371. 1371. 1371. 1371. 1371. 1371.53 1971. 1971. 1971. 1371.33 1371.30
LINES 50500-
82
62 03 SO 30 46 45 44
08 03 03 01 SO SO 74 74 72 53 56 34
2-O 2-O 2-O 2-O 2-O 2-o 2-o 2-o 2-O 2-O 2-O 2-O 2-O 2-O
P P R R R P P P R R R P P P
7 7 3 3 9 5 5 5 7 7 7 3 3 3
2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 5-l 5-l 5-l 5-1 5-l 5-l 3-o 3-o 3-o
R 5 R 5 R 5 P 1 R 3 R 3 R 3 0 1 R 1 R 1 PlS PlS PlS R21 R21 R21 P23 P23 P29
M. NISI ET f?t d.
1048
and Figs la, b, c and d) corresponds mainly to the 20 band with an effect of the 51 band at 300 K. The experimental structure for absorption less than 2 x 1O-23cm* is due to laboratory noise. The effect of the underlying Herzberg continuum is important since it can be detected easily by the differences of + 10 and +20% illustrated in Fig. lb, particularly by the absolute values of the absorption cross-section with and without continuum at 270 and 190 K as depicted in Figs lc and Id.
The spectral interval 51,750-52,000 cm-’ is characterized by linewidths (Av = 3.6 cm-‘) of the rotational lines of the 4-O band (Table 7). These lines play a very important role in the overall pattern of absorption (Fig. 2a), since the effect of the Herzberg continuum is negligible and produces practically no variation when the absorption cross-section is varied by f 10 or +20%. The variation of the absorption cross-section with temperature (T = 300, 270, 230190 K) illustrates the decreasing role of the 7-l band
TABLE7. IDENTIFICATION 0~0~ SCHUMANWRUNGEROTATIONAL LINES 5175C 52000cm-’
7 9
51787.1 51787.4 51788.0 51796. 0 51796.3 51797. 0 51798.7 51798. 8 51799.3 51800 51825. 4 51825. 5 51826. 0 51829.3 51829. 5 51830.1 51850 51852. 7 51853. 0 51853.6 51855.0 51855.1 51855. 5 51862.6 51862.6 51863. 1 51865.9 51866. 1 51866. 7 51894. 3 51894.3 51894. 7 51897.1 51897.3 51897.8 51900 51903. 6 51903.8 51904. 3 51905.5 51905.6 51906. 0 51908.9
1931. 15 1931.
”
band
A 5*;50 51782. 51782. 51783.4
14
4-O 4-O
PI5 P15
4-o P15
1931.12 1930.98 1930.97 1930.95 1930.65 1930.64 1930.61 1930.55 1930. 55 1930.53
4-o R17 4-o R17 4-o R17 7-l R21 7-1 R21 7-l R21 7-1 P19 7-1 P19 7-l Pl9
1929.56 1929. 55 1929.54 1929. 41 1929.40 1929.38
4-O 4-O 4-O 4-O 4-O 4-O
P13 P13 P13 R15 R15 R15
1928. 54 1928. 53 1928.51 1928.46 1928.45 1928. 43 1928.17 1928.15 1928.05 1928. 04 1928. 02 1926.99 1926.99 1926. 98 1926.89 1926.88 1926.86
7-l 7-l 7-l 7-l 7-l 7-l 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O
R19 R19 R19 P17 P17 P17 PI1 Pll Pll RI3 R13 R13 P 9 P 9 P 9 Rll Rll Rll
1926.65 1926.64 1926. 62 1926.58 1926.57 1926. 56 1926. 45
7-l 7-l 7-l 7-l 7-l 7-l 5-O
RI 7 R17 R17 PI 5 P15 P15 P29
1929.17
51909.1 51909.
51911. 51911.9 51912. 51920. 51920.6 51920. 51922. 51923. 51923.5 51941.3 51941. 51941, 51943. 51943. 51943. 51948. 51948. 51949. 51950 51950.2 51950.3 51950.6 51956. 51956.6 51957.1 51957. 51957. 51958. 51966. 51967. 51967.2 51967. 51969. 51971. 51971. 51987.8 51987. 51988. 51989. 51989.
band
b
7
4 5 5 9 9 0
3 7 1 2 6 6 8 3
6
9 9 4 4 2 6 4 0 0 9 4 1 1
51989.5
51989. 7 51990. 4 51991.2
1926. 1926.
45 42
5-O 5-O
P29
7-l 7-l 7-l 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 7-l 7-l 7-l 7-l 7-l 7-1 8-l 8-1 8-l
P13 P13 P13 P 3 P 3 P 3 R 5 R 5 R 5 P 1 R 3 R 3 R 3 0 1 R 1 R 1 R13 R13 R13 Pll Pll Pi1 R29 R29 R29
P29 1926.36 8-l P29 1926.34 8-l P29 1926. 32 8-l P29 1926. 02 4-O P 7 1926. 02 4-O P 7 1926. 01 4-O P 7 1925. 93 4-O R 9 1925. 93 4-O R 9 1925. 91 4-O R 9 1925.25 4-o P 5 1925.25 4-O P 5 1925. 24 4-O P 5 1925. 18 4-O R 7 1925.18 4-O R 7 1925. 16 4-O R 7 1924. 98 7-l R15 1924. 97 7-l R15 1924. 96 7-l R15 1924.92 1924.92 1924. 90 1924. 68 1924.68 1924. 67 1924. 64 1924. 63 1924. 62 1924. 32 1924. 29 1924.29 1924.27 1924.21 1924. 15 1924. 15 1923. 53 1923. 52 1923.51 1923. 48 1923. 48 1923.47 1923. 46 1923. 43 1923. 40
1049
Aeronomic problems of oxygen photodissociation(Fig. 2b) and the change in the structure of the 4-O band at high rotational levels, PlSR17. In the 54,00&54,250 cm-’ interval, the principal contribution to the total absorption cross-section to the Pl-P13 lines of the 8-O band with an additional effect of the 12-1 and 13-1 bands (Fig. 3a). There is no contribution of the continuum (6 x 10mz4cm’) since the minimum cross-section is not less than 5 x lO_” cm2. The variation of the structure (Fig. 3b) is associated only with the rotational and vibrational populations related to temperatures 300-190 K, particularly in the 54,15@-54,250 cm-’ region corresponding to the lines of the (12-l), (13-1) and (14 1) bands. It seems, therefore, that there is a remarkable agreement between the experimental and theoretical crosssections. Yoshino et al. (1983) estimate that the error in the spectral range 60 to 12-O bands may vary from about 5% in regions of the principal absorption peaks to about 10% in window regions and that errors in the range of the absolute cross-sections below 1O-22 cm2 could be somewhat greater. In any case, our detailed modeling procedure in which the cross-sec2-o
6. THE SCHUMANN-RUNGE
BANDS AT 79 K
The recent experimental determination by Yoshino et al. (1987) of the cross-sections at 79 K with an instrumental bandwidth of 0.4 cm-’ has been compared with a theoretical calculation based on the spectroscopic parameters adopted at 300 K. We present our comparison in graphical format with a semilogarithmic plot for the 2-O bands through 12-O with a complete assignment of all rotation lines (Figs 4-14). According to Yoshino er al. (1987), their experimental values of the absolute absorption cross-sections would be of the order of 4% in regions of the principal absorption peaks while the errors in the range below 5 x 1O-22cm-’ should be greater (limited column den-
CROSS-SECTION T
-20 r
Rl7
j
R5 P13
P25 -21
tion is computed as a function of wavenumber for lines with Voigt profiles and in which predissociation line widths are treated as parameters produces excellent agreement with the best experimental data independent of the instrumental width. It is also justified by a comparison of the theoretical and experimental cross-sections at 79 K.
;pll
. . . . . . .. LABORATORY
WARVAkD)
e
BFNJSS$LS)
CALCUiATION
Rl’Ij
/ RI3
P9
R9
P7
R7
P5
h
3 -23
-24 50
3
79 K
50550
50600
URVENUIlBER
50650
50700
24 BAND AT 19K. less than 5 x 1O-23 cm’ in the laboratory noise. Agreement and experimental peaks.
50750
FIG.~.AENRFTIONCROSS-SECTIONSOFTHE
Experimental
cross-sections
between theoretical
3-o
51150
79
CROSS-SECTIPI
K
59200
51250
URVENUHBER
51 JO0
5,350
FIG.% ~sORFT~ONCROSS-SECTIONSOPTHE ~~BANDAT~~ K. Rotation linesof ‘60’80 isotope with spikesfor cross-sectionsnot lessthan 5 x IO-” cmz.
5,750
79
5,800 K
51850
WRVENWIBER
5,900
FIG. 6. ABWRPTION c~oss-_swr~o~OFTHB4-O BAND AT79 K. Linewidthdeterminedat 300K in agreementwith structureat 79 K.
5
00
5-o
1051
CROSS-SECTION
-19
-20
;;
0 fu-21 Tii
3 -22
-2: 5:
10
79
52450
K
WAVENUMBER
52500
FIG.~.AJSORPTION CROSS-sEcnoNSOl'THE~BANDAT79K. Underlying continuum (0.7 x 1O-23 cm*) without any effect.
..f....
_-20
LAyRAT0RY. 1 CAijCULAiloN j :
8 z
I !
:
/ :
-‘CON-iINUlJM_7ix 162%m2
6 ;_
R
,!
-22
x
“0
%’
LINES
“A#.-
I.Pa
; iW.-l&m^l
I”
i I
FIG.~.AWXPTIONCROSS-SECTIONSOFTHE~~BANDAT~~K. Spikes corresponding to ‘60’80 lines clearly apparent between 160, lines below the “O”O
head.
7-o
CROSS-SECTION --
j-..
__ -Ftn
.P9
.22
-23 5:
I= 5o
79
1:
-iFI9 i. !P7
fi7-: ..P5.
‘R5 $?2Rl _._j _
j O.Sr34x1(
53500
53550
K
53600
I :
jS.1
”
i L.W,-l.Qcm”
-: : ._
i
i
-/
/
53650
-I
I 53700
WRVENUIIBER
FIG. 9. ABSORPTIONCROSS-SECTTIONSOFTHEI 7-O BAND
Laboratory noise still noticeable near lo-”
.23 5: '
54000
79
K
54050
54100 URVENUHBER
AT 79K. cm’.
54150
5
COO
~G.lo.~~~ON CR~-~~ONSOF~8~B~AT79 K. Apparent anomaly between P13 and Pt5 lines as a result of the laboratory limited cohmm density.
9-o iii
1053
CROSS-SECTtal
-1s
R15 I P13
Pl5
Ril i RQ PQ 1
R13 iPl1
R7’ /R5. R$Rl P5 ! kP3.A
-19
_ -20 8
z f ;;
18~
-22
!‘80
-3 0
79
54450
K
FIG.
54500
11. ABSORPTION
LINES
:
* L .W.==l .acti’
i 1
59550
WAVENUHBER
CROSS-SEC~ONS
:; CL%-l.0xld5
0F THE 9-O BAND
AT
79 K.
Superposition between P13 and R13 lines of 160”0 spikes and laboratory noise, >S x lo-” < 1O-22cm’, respectively. 10-O
54
54600
cm* and
CROSS-SECTION
-1s
-23 54010
79
K
54850
FIG. 12.ABSORPTION
59950 WAVENUt-lBER CRW-SECTIONS
OF THE 1fM
55000
BAND AT
55050
79 K.
All aspects described in Figs 4-10 present in a comparison of theoretical and experimental structures.
1054
11-O
m7
..: P15
-22 55200 79
K
.I
ms_
55250
.:. :. P13.
55300
WRVENUIIBER
55350
55400
FIG. 13. ABWRPTION CR~SXIXTIONS OFTHE1IHI BANDAT 79 K. Remarkable differences in structure above and below ‘60’*0 head. 12-o
CROSS-SECTlaJ
-17
-18
_-1s 8
z f s
q-20
-21
-22 55
FIG. 14. ABWRPTIONCROSS-SECTIONS OFTHE12-O BAND Last band with experimental cross-sections.
AT
79K.
1055
Aeronomic problems of oxygen phot~issociation-~~ 54000-54250Cm-’
TABLE%IDENTIFICATTONOF02S CHUMANN-RUNGEROTATIONALLINES
5dhw 54000.0
54000.2 51000.5 54003. 54004. 5dOO5.4 51006. 54005. 54035. 54036.4 54036. 54437. 54035. 54039. 51040. 5dOdO. 54040.9 5##41,2 54044. 54050 54051.2 54054.4 54456. 54456. 54057.2 54057. 54062. 54063.2 54063. 51071. 54072. 54072. 54075.5 54075.6 54075. 54078.2 54075. 54479. 54084.9 51086. 54087.3 54087. 54088. 54050. 54090.6 54092.0
7 e 9 6 9 6 0 0 4 0 a
0
0 5 5 6 7 5 0 3
9 7 0 Q a 0 6
band
1 1551.55 1553.55 155I.54 3553. 73 1553. 65 1551.67 3553.62 1551. 56 3550. 62 3550.61 3550. 60 1550.59 3550.55 1550.50 1550.45 1560.45 3550.45 1a5v. 44 1550. 34
6-V 5-V a-o 12-f 32-f 12-f 33-f 33-I id-1 a-o a-a 8-O fz-I 12-f 12-3 5-V 34-f a-v 14-l
PI3 P33 P?3 P35 PI5 PI5 f23 P23 P27 R33 Rf3 a13 a35 R15 a15 PI? P27 Plf P27
1550. 1549.
13-l 13-l 32-i 13-1 32-3 12-f S-O S-O S-O a-o 5-o 5-V B-O 5-O 3-O 9-V 9-O S-O
R23 R23 P13 R23 P33 P?3 W7 RZ7 R27 a11 RI? Rt? P 9 P 9 P 9 p25 P25 P25
30 99 1649. 93 1549. 92 3549.59 1a49.5a 1549. 71 1849. 69 fa49. 67 I549.39 1349.39 1549.38 lads. 27 1849.26 1549.25 1519. 37 1849.16 lad9. 35 ia45.95 Iada. 93 1548.56 1545.55 1548. 54 1545. 75 1545. 75 fada. 70
ld-1 R/7
12-l 12-f 12-f 13-f 14-l 33-l 33-f
R33 R33 a13 P21 ff27 F23 PZ?
54092. 54094. 54100 54100. 54101. 54141. 5df VI. 54101. 54102. 5dl02. 54104. 54104. 54104. 51324. 54324. 54124. 54126. 54326. 54326. 54127. 54125.2 54328. 54131. 54134. 54336. 54135. 54139. 54139.9 54140. 54341. 54141.4 54141. 54141. 54142. 54143. 54143. 54113. 54144.3 54144.4 54144. 54147. 54147. 54150 54152. 54152. 54152.
band
1
”
9 3
1645.67 15-l 3648. 62 14-3
8 f 3 d 6 6 7 0 f 4 3 d 7 5 6 9 0
1546.40 1545.39 3545.33 3545.38 1545.35 1548.34 l545.34 f&IS. 29 1845.29 1545.25 1547. 60 1547.59 1547.55 1547. 52 1547. 52 1647.51 1547. 51 f547. 47 3547. 45 1547.35 1847.26 1547.20 1847. ?I 1547.07 1547. 07 3547. 03 1547.03
6 5 d 1 6 5 9 0
15-3 5-o a-o f2-I 5-V 12-I 12-f 8-V B-O 5-O 5-V 5-V a-o 5-V a-0 5-o 12-1 32-I 12-f 13-I 13-f 33-I 15-f
P29 R27 P29 R 9 R 9
Pff
32-l 12-i
R 9 PI1 PI1 P 7 P 7 P 7 R 7 R 7 R 7 P 5 p 5 P 5 Rl? RI? RI1 R23 RZ3 R21 a29 P25 P 9 P e
12-l
P 9
14-l
t5dz
0.2 8-o a
01 00 96 96 94 ed
4
3547. 1547. 1516. 1546. 1546. fad6. 1546.92 Ii346. 3546.eV 1546.52 1516.
4 5 9
5 8 9 V 5 7
7
f
Bf
8-O 5-O 5-O 8-O 5-O 9-V 9-V 34-3 s-o 14-3 15-l
5 R 5 R 5 P 3 P 3 P 3 a25 a26 P25 a25 P25 a29
1546. 64 1546. 64 1546.62
5-V 5-V 5-V
R 3 R 3 R 3
sity). This is the explanation of the strong noise (loga~~c scale) in the figures ~o~es~on~ng to 2-O and 3-O where the continuum cross-section is less than 5 x 10-23 cm2. Spikes which are clearly apparent in the experimental data, from the 6-O to 12-O bands, between the principal lines shown with their assignments are mostly rotational lines of the isotopic molecules ‘60*80. These spectral features are shown in the vari-
91
”
1
54353. 3 I546. 62 1546. 62 54153.1 54155. a 1546. 52 543 57.2 1546. 45 54157. 4 1546. 47 54155. 0 1546. 45 lad& 44 54355.4 54158. I 1546. 43 54363. 3 1846.35 54362.1 1546.31 54162. 4 1546. 30 54164. 6 1546. 22 54167. 0 1846.14 54165. 1 3546. IV 54171. 5 1545. es 54372. 4 1845. 96 64172. 5 1545. 96 54355.5 1545. 50 51155.2 1545. 42 54159.2 1545. 39 54159.4 1545.38 54190. 9 3545. 33 541.94. f 3545.22 54196. I 3545.15 54197. 0 3545. 32 54197. I 1545. I2 54200 54204.2 1544. 55 54206. 9 1544. 79 54205. 4 15dd. 73 54205. 4 ISdd. 73 54209. 3 1844.70 54209. 5 1544.70 54210. 7 3844. 65 54213. 5 1544.55 5121d. 7 1544.52 54215.2 1544.50 5dZI7. 5 I5dd.42 51217. 9 IBId. 41 54215.4 1844. 39 54239. V fadd. 37 54219. 4 f544. 36 54221. 6 15dd.25 54222.2 2541.26 54222. 5 1844.25 51222.5 I5dd. 24
band
5-O 15-f 5-O 5-O 5-O 9-O 9-V 3-O 12-Z 32-f 12-3 33-3 13-l 13-1 12-l 32-l 32-i 14-f 12-l 12-1 12-f 14-3 14-l 32-l 32-l 12-1
P I R29 V 1 R 1 R 1 P23 P23 P23 R 9 R 9 R 9 PI9 P19 P?9 P 7 P 7 P 7 R25 R 7 R 7 R 7 R25 R25 P 5 P 5 P 5
13-I 13-l t3-1 12-f 1.2-f 12-f 15-3 12-l 12-l 12-f 16-l f5-I S-V S-V 3-O 32-f 15-I 12-I 12-f
RlS RI9 /??9 R 5 R 5 a 5 f’27 P 3 P 3 P 3 P29 P27 R23 R23 R23 R 3 I’27 a 3 R 3
ous figures with an indication of the heads of the %‘*O bands. We have verified our assigmnents thanks to unpublished data (Yoshino-Egmont, personal communication). As an example, the crosssections of the 8-O bands of 160, and ‘60’80 are compared in Fig. 15. It is clear that the four spikes (see Fig. 10) in the window between the P9 and Pl 1 lines of 1602near 54,050 cm-’ correspond to tire first lines of the r60’80 molecules and that the two groups
1056
CROSS-SECTION
-22
/
-23 53950 79
I
54000
K
54050
I
I! WAVENUtlBER
541p
ds150
54200
FIG. 15. ALSORPTION CROSS-SECTIONS OF THE 160, AND‘60’80 BANDS AT 79 K. Comparison between ‘6O’8Oexperimental and 1602theoretical determinations. 300 K
CROSS-SECTION
R17 1 P15 I
150 0
79
K
50550
R15 P13
j R13 i .Pll
50600
2-o
Ril i P9 /
WAVENUMBER
50650
R9 P7
R7 -d5 R3Rl P5 P$ p1
50700
-- --
5
‘50
FIG. 16. ROTATIONAL STRUCTURES OFTHE2-O BAND AT 300 AND 79 K. At high rotational levels, upper curve for 300 K and lower curve for 79 K. At P7-R9 lines, beginning of an inverted position for both curves.
1057
Aeronomic problems of oxygen photodissociation-
R17 i ---
0
79
K
R,5 --‘i
51800
51850
Fill
R13
WAVENUMBER
51900
R9
R7i
51950
R5-R3Rl
1
52000
FIG. 17. ROTATIONAL STRUCTURES OFTHE40 BANDAT 300 AND79 K. At high rotational levels, upper curve for 300 K and lower curve for 79 K. At P7-R9 lines, beginning of an inverted position for both curves.
with a double structure between the Pl 1 and P13 lines of ‘“02 near 54,025 cn-’ belong to the 160180 isotopic molecule.
7. COMPABIBON BETWEEN THE
ARSORPTION
STRUCTURES AT 300 AND 79 K
The theoretical cross-sections of the (2-O) to (120) bands at 300 and 79 K have been compared. Two examples are shown in Figs 16 and 17 for the 2-O and 4-O bands. Details of the line assignments (Yoshino ef al., 1984; Nicolet et al., 1987) show (see Figs la and 2a, respectively) that the main apparent differences are due to the temperature contrast, specifically the disappearance of the lines corresponding to u” = 1 and the decrease of the intensity of the line corresponding to a” = 0 at relatively high rotational levels (see Tables 6 and 7). This means that the absorption cross-sections at 79 K as shown in Figs 4-14 are practically free from any lines of other bands, and they increase on the lower rotational levels.
8. CONCLUDING REMARK The high resolution absorption cross-section measurements made by the Harvard-Smithsonian group at 300 and 79 K of various bands of the Schumann-Runge system of O2 have allowed the calculation of linewidths of rotational lines for which the band oscillator strengths were obtained. An accurate calculation of the band structures at various atmospheric temperatures may be performed when adequate averaged linewidths are determined for each band.
Acknowledgements-This work is based not only on the most recent publications available, but also on unpublished experimental data. Our special thanks go to the members of the Harvard-Smithsonian Croup who have kindly provided such data. Support for the preparation of this work has been facilitated by grants from the Commission of the European Communities, Directorate-General for Science, Research and Development, Environment Research Programme, of the Office of Naval Research contract NOO14-86-K-0265WOO2 with the Communications and Space Sciences Laboratory of Penn State University, and of the Chemical Manufacturers Association Contract FC 85-563 with the Institut d’Abronomie Spatiale.
M. NICOLETet al.
1058 REFERENCES
Ackerman, M. and Biaume, F. (1970) Structure of the Schumann-Runae bands from the (M)) to the (13-O) band. J. Molec. gpectros. 35, 73. . ‘ \ * Allison, A., Dalgamo, A. and Pasachoff, N. W. (1971) Absorption by vibrationally-excited molecular oxygen in the Schumann-Runge continuum. Planet. Space Sci. 19, 1463. Biaume, F. (1972) Determination de la valeur absolue de l’absotption dam les bandes du Systeme de SchumannRunge de l’oxygene moleculaire. Aeronomica Acta, Brussels, A, no. 100, l-270.
Brix, P. and Herzberg, G. (1954) Fine structure of the Schumann-Runge bands near the convergence limit and the dissociation energy of oxygen molecule. Can. J. Phys. 32, 110. Cheung, A. S.-C., Yoshino, K., Parkinson, W. H. and Freeman, D. E. (1984) Herzberg continuum cross section of oxygen in the wavelength region 193.5-204.0 mn and band oscillator strength of the (O-O) and (la) SchumannRunge bands. Can. J. Phys. 62, 1752. Cheung, A. S.-C., Yoshino, K., Parkinson, W. H. and Freeman, D. E. (1986) Molecular spectroscopic constants of O@;), the upper state of the Schumann-Runge bands. J. molec. Spectrosc.
119, 1.
Fang, T. M., Wofsy, S. C. and Dalgamo, A. (1974) Opacity distribution functions and absorption in SchumannRunge bands of molecular oxygen. Planet. Space Sci. 22, 413. Lewis, B. R., Berzins, L. and Carver, J. H. (1986a) Oscillator strengths for the Schumann-Runge bands of 1602. J. Quant. Spectrosc. Rad. Trans. 36,209. Lewis, B. R., Berzins, L., Carver, J. H. and Gibson, S. T.
(1985a) Decomposition of the photoabsorption continuum underlying the Schumann-Runge bands of %-
I. Role of the B3Z state. I-A
new dissociation limit. J. Quant. Spectrosc. Rad. Trans. 33,627. Lewis, B. R., Berzins, L., Carver, J. H. and Gibson, S. T. (1986b) Rotational variation of predissociation linewidth in the Schumann-Runge bands of 1602 J. Quunt. Spectrosc. Rad. Trans. 36, 187. Lewis, B. R., Berzins, L., Carver, J. H., Gibson, S. T. and McCoy, D. G. (1985b) Decomposition of the photoabsorption con&u& underlying the SchumannRunae bands of ‘6O,-II. Role of the 1% state and collision induced absorption. J. Quant. Spectrosc. Rad. Trans. 34,405.
Nicolet, M., Cieslik, S. and Kennes, R. (1987) Rotational structure and absorption cross sections from 300 K to 190 K of the Schumann-Runge bands of OZ. Aeronomica Acta, Brussels. A, no. 318, I-340. Nicolet, M. and Kennes, R. (1986) Aeronomic problems of the molecular oxygen photodissociation-I. The 0, Herzberg continuum. Plunet. Space Sci. 34, 1043. Nicolet, M. and Kennes, R. (1988) Aeronomic problems of molecular oxygen photo-dissociation-IV. The various parameters for the Herzberg continuum. Planet. Space Sci. 36, 1069.
Yoshino, K., Freeman, D. E., Esmond, J. R. and Parkinson W. H. (1983) High resolution absorption cross section measurements and band oscillator strengths of the (1, Ok (12,O) Schumann-Runge bands of Or. Plunet. Space Sci. 31, 339. Yoshino, K., Freeman, D. E., Esmond, J. R. and Parkinson, W. H. (1987) High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge bands of oxygen at 79 K. Planet. Space Sci. 35.1067. Yoshino, K., F&man, D. E. and Parkinson, W: H. (1984) Atlas of the Schumann-Runge absorption bands of O2 in the wavelength region 175-205 nm. J. phys. Chem. Ref. Data 13,207.
W32-0433/88 53.W+O.O0 Pngamon Pros pk
AERONOMIC PROBLEMS OF MOLECULAR OXYGEN PHOTODISSOCIATION-II. THEORETICAL ABSORPTION CROSS-SECTIONS OF THE SCHUMANN-RUNGE BANDS AT 79 K MARCEL NKOLET,* STANISLAS-IJRt amdROBERT RRNNES Institut d’Mronomie Spatiale de Belgique, 3 Avenue Circulaire, B-l 180 Brussels, Belgium (Received 22 April 1988) Alrstraet-Theoretical spectra corresponding to the domain of the rotation lines of the 2-O to 12-4 bands of the B%;-X%; Schumann-Runge system of O2 at 79 K are presented in graphical format. Calculated absorption cross-sections are compared with recent laboratory measurements made at the same temperature. The calculations were based on previous theoretical detonations at 300 K established after a comparison with results of laboratory measurements made at the same temperature. Such an analysis in which the band oscillator strengths are associated with averaged linewidtbs of the rotation lines for each band and with their underlying continuum, gives consistent values for the various spectroscopic parameters
of the O2 !Mnunann-Runge bands.
1. ~RO~U~ON
In a recent publication (Nicolet et al., 1987),a theoretical determination of the rotational structure and absorption cross-sections of the O2 Schumann-Runge bands (see Table 1) was made at 300 K. This detailed analysis was based on the experimental results obtained by the Hazard-S~thso~an Group on the photodissociation absorption cross-sections at high resolution in the spectral region corresponding to the u’ = 1-12 bands (Yoshino et al., 1983). After the first detailed analyses such as the wavelength assignments, for u’ 2 12, of Brix and Herzberg (1954) and, for u’ < 13, of Ackerman and BiaumC (1970) and Biaume (1972), extensive wavenumber measurements of the rotation lines of the O2 Schumann-Runge absorption bands were provided by Yoshino er al. (1984). These sets of data are also the most accurate and most complete since the crosssections are absolute, the line~dths being in excess of the instrument resolution for the various bands studied. Recent rotational constants (Table 2) of the upper electronic state of the Schumann-Runge system have also been published by Cheung et al. (1986). These *Also with: Communications and Space Sciences Laboratory, Penn State University, University Park, PA 16802, U.S.A. t Now at : Commission of the European Communities, ISPRA Establishment, Italy, Chemistry Division, Air Pollution Sector.
constants make it possible to calculate the wavenumbers of the rotation lines. The same spectroscopic constants have been also determined by Lewis et al. (1986a,b) from the wavenumber measurements of Yoshino et al. (1984). The adopted band oscillator strengths of the (u’, 0) and (v’, 1) bands were based on the various results of Yoshino et al. (1983), of Cheung er ai. (1986), and of Lewis er al. (1986a). The mean predissociation linewidths were determined after a detailed comparison between calculated absorption cross-sections and the experimental results pub~shed by Yoshino et al. (1983) in the spectral region corresponding to the U’ = 1-12 bands. However, the absorption cross-sections throughout this region may depend also on the underlying continuum corresponding near 50,000 cm-’ to the O2 Herzberg continuum (see Nicolet and Kennes, 1986, 1988a). At wavenumbers greater than 55,000 cm-’ , the OZ Schumann-Runge wntinuum (see Lewis er al., 198Sa,b) plays a role related to the temperature. The recent extensive determination by Yoshino et al. (1987) of the experimental structure of the 2-O to 12-O bands at 79 K provides a direct test for the theoretical determination which must be used for aeronomic purposes (tem~rat~es generally between 170 and 270 K). In the present paper experimentai data and theoretical results at 79 K are compared to provide an improved understanding of the absorption structure in the predissociation region of the O2 Schumann-Runge system.
1039
1040
M.
NICOLET
et al.
TABLE 1. ADOPTED SPECTRALINTERVALSFOR THE SCHUMANN-RUNGE BANDS OF O2
Band
Wawnuabw
(cm-')
Wav*lsngth
Mean
(rim)
M*an
Ai
49000-49500
49250
500
204.08-202.02
203.04
2.06
I-O
49500-50050
49777
550
202.02-199.80
200.90
2.22
2-o
50050-50715
50382
665
199.80-197.18
19a.48
2.62
3-0
50715-53355
51035
640
197.18-194.72
195.94
2.46
4-O
51355-51975
51665
620
194.72-192.40
193.55
2.32
5-O
51975-52565
52270
590
192.40-190.24
191.31
2.16
6-O
52565-53130
52847
565
190.24-188.22
189.22
2.02
188.22-186.36
187.28
1.86
o-o
7-o
53130-53660
53395
530
8-O
53660-54160
53910
500
186.36-184.64
185.49
1.72
9-O
54160-54625
54392
465
184.64-183.07
183.85
1.57
to-o
54625-55055
54840
430
183.07-181.64
182.35
1.43
II-O
55055-55440
55247
385
181.64-180.37
181.00
1.27
179.80
1.13
12-o
55440-55790
55615
350
180.37-179.14
13-o
55790-56090
55940
300
179.24-178.28
178.76
0.96
14-o
56090-56345
56217
255
178.28-177.48
177.88
0.80
15-O
56345-56550
564Jk7
205
177.4a-176.83
177.16
0.65
16-0
56550-56725
56637
175
176.83-176.29
176.56
0.57
17-o
56725-56855
56790
130
176.29-175.89
176.09
0.40
175.72
0.33
775.45
0.23
18-0
56855-56960
56907
105
?75.89-175.56
19-O
56960-57035
56997
75
175.56-175.33
2. THE BAND OSCILLATOR
STRENGTHS
The Schumann-Runge bands, analyzed many times, have generated several determinations of their mean oscillator strengths. The values adopted here (Table 3) are based mainly on the recent results of the Cambridge and Canberra groups to generate a consistent set of data (Yoshino et ul., 1983 ; Cheung eta& 1984;Yosbinoetaf., 1987; Lewisetal., 1986a,b) and also on the analysis of Allison et al. (1971). Since it is practically impossible to introduce an exact oscillator strength adapted to all circumstances, mean values have been adopted for each vibrational level. The uncertainties should be generally less than 5% but could reach perhaps 5-10% for two or three bands. In any case, the values given in Table 3 must be considered as averaged band oscillator strengths to be adopted in order to determine the effective linewidths of the rotational lines of bands corresponding to the various vibrational levels from U’ = 0 to v’ = 19.
The measured high resolution absorption crosssections of the Schumann-Runge bands by Yoshino et al. (1983) between 201 and 179 mn have been adopted to determine the effective rotational linewidths. Even when experimental results exhibited systematic variations with rotational levels (Lewis et al., 1986a,b), an equivalent band linewidth was adjusted to fit the experimental absolute cross-sections after the introduction of the effect of an underlying continuum. The He&erg continuum plays an important role in the determination of the absorption cross-sections of the first Schumann-Runge bands. The SchumannRunge continuum is subject to a variation related to the population of the rotational and vibrational levels in the spectral range of the last bands near the normal continuum limit. The best-fit model calculated values of the O2 absorption cross-sections with the experimental
Aeronomic problems of oxygen photodissociationTABLE2.
hOPTED
1041
SPECTROSZOPIC CONSTANTS FOR THE UPPER STATE OF THE %XUMANNRUNGEBANDSOF 0,m COMPUTELINEPOSITIONS
Band
vo(cm-‘)
B ”
o-o
49357.96
0.8132
D ”
x
4.50 x 1O-6
”
1.69
y,
- 2.80.~.10-~
1-o
50045.53
0.7993
4.20
1 .70
- 2.60
2-O
50710.68
0.7860
5.80
1.69
- 2.90
3-O
51351 .94
0.7705
5.20
1.70
- 2.60
4-o
51969.36
0.7550
5.97
1.81
- 3.00
5-o
52560.94
0.7377
5.80
1.75
- 2.20 - 2.10
6-0
53122.65
0.7187
5.00
1.79
7-o
53655.95
0.7010
8.60
1.82
- 2.10
8-0
54156.22
0.6770
6.70
1.91
- 2.30
9-O
54622.50
0.6514
6.30
2.04
- 2.10
10-O
55051.16
0.6263
9.90
2.10
- 4.10
11-O
55439.23
0.5956
9.40
2.17
- 3.80
12-o
55784.58
0.5626
1.37 x 1O-5
2.37
- 5.40
13-o
56085.44
0.5242
1.63
2.51
- 8.40
14-o
56340.42
0.4832
2.09
2.81
- 1.16 x lo-'
15-o
56550.62
0.4391
2.54
3.30
- 1.64
16-0
56719.62
0.3934
3.08
4.11
- 2.41
17-O
56852.45
0.3457
3.34
5.18
- 3.48
18-O
56951.60
0.2872
5.50
6.51
- 4.94
19-o
57025.80
0.2649
6.00
7.63
- 6.04
- band origin = T + $AY as given by Cheung et al. “0 constants for vibrational 1~~1s Bv and DV - rotational
xv and Yv splitting For 18-O and 19-0,
constants see
Fang,
for
levels.
Wofsy and Dalgarno
have been used to determine the rotational linewidths adapted to each band. The adopted mean rotational linewidths are given in Table 4. The computation was made at each 0.1 cm-’ with a contributing spectral range of 500 cm-’ for a Voigt profile. Since realistic high resolution synthetic spectra require line centers to be located to within about 0.1 cm-‘, the wavenumbers obtained at each 0.1 cm-’ between 49,000 and 57,000 cn-’ give the possibility of determining the detailed structure of the whole spectrum and of studying the effect of temperature. In addition, the relative role of the underlying con-
measurements
vibrational
(19%)
(1974).
tinua with their related accuracy can be investigated
as a function of temperature and wavelength. 4. THE O2 HERZBRRG
CONTINUUM
The absorption cross-sections of the O2 Herzberg continuum at wavelengths greater than 200 nm used before 1980 must now be replaced by experimental and observational results obtained recently (1984-1986). An analysis made by Nicolet and Kennes (1986, 1988) leads to the adoption of an empirical formula for the absorption cross-section,
M. NICOLETet al.
1042
TABLE3. f&PTFD MEAN ABWRPTIONGK!ULATORSTRENGTIS j&,, FORTHEs CHUMANN-RUNGEBANDS OF o2 DEDUCED FROM ABSORPTION
fw
Vf
0 1
$.;;
2 3 4 5 6 7 8
1.9 x 8.2 x 2.7 x 7.4 x 1.6 x 3.4 x 6.2 x 1.0 x 1.5 x 1.9 x 2.4 x 2.7 x 2.8 x 2.7 x 2.6 x 2.2 x 1.7 x 1.3 x
1; II 12 13 14 15 16 :i 19
SPECTRA
w;
7.6 x lo-9
lo-* lo-8 1O-7 lo-7 lo+ 1o-6 IO-’ lo+ 10-j lo-5 IO-’ IO-’ l0-5 lO-5 lO-5 lo-’ lo-J Io-5
8.2 x 4.6 x 1.8 x 5.0 x 1.3 x 2.7 x 5.0 x 8.6 x 1.2 x 1.7 x 2.1 x 2.6 x 2.6 x 2.9 x 2.7 x 2.0 x 1.6 x 1.3 x 1.6 x
cTHER(OZ)= 7.5 x lo-2yv/5 x
l-id lo-* lo-’ lO-6 lo-6 lo-s IO-’ lo-5 lo-5 lo-4 lo-4 lo-4 IO-4 lO-4 lo-‘+ lo-“ lo-4 lO-4 lo-4 lO-4
x 104)
are given for spectral intervals of 500 cm-‘, mean absorption cross-sections of the O2 Herzberg continuum are used in our computations. The adopted numerical values are given in Table 5. 5. ANALYSIS
OF THE PHOTOABSORPTION CROSS-SECTIONS
In our general analysis (Nicolet et al., 1987), the line positions and rotational assignments are reproduced for intervals of 250 cm-’ and the theoretical and experimental absorption cross-sections are presented graphically (1 cm-’ per mm) at 300 K throughout the 49,000-57,000 cm-’ wavenumber region corresponding to all bands with u’ = O-19 and v” = 0 and I. This graphical comparison between the calculated and measured absorption cross-sections begins at 49,750 cm-‘, 1-O and 3-l bands, and ends at 55,800 cm-‘, 12-O and 19-1 bands. In order to show the principal features of the spectrum, three different regions (rotational lines with their identifications in Tables 6,7 and 8) are illustrated in various figures by a ~~-lo~~t~c plot of the absorption cross-sections, namely between 50,500 and 50,750 cm-’ (Fig. la), 51,750 and 52,000 cn-’ {Fig. Za), and 54,000 and 54,250 cm-’ (Fig. 3a). Such
exp { -5O[in (v/(5x 104)12)cm-‘.
Although the available sets of Herzberg continuum cross-sections derived from laboratory measurements seem to reach an acceptable agreement with their experimental accuracy at wavelengths greater than 200 nm, the errors of the experimental or theoretical determinations prevent an exact extrapolation for the Herz&rg con~nu~ underlying the SchumannRunge bands between 190 and 200 nm. Nevertheless, the stratospheric determinations are not in disagreement with the values deduced from the formula that we have adopted. Since our final determinations of the oxygen transmittance and of the photodissociation rate constants
TABLE 4. ADGPTED MEAN ROTATIONLI~~DTHS ~-RAGE BANDSOF O2 0’
cm-’
d
0
8 0:6 1.8 3.6 2.0 :*t 2:1 1.2
Cross-sections
(cm-‘)
(cm3
Interval (cm-‘)
Cross-section (cm3
49,~9,~
7.2 x lo-=
52,000-52,500
7.2 x lo-=
50,00(t50,500 49,500-50,000 50,50~51,000 51,00&51,500 51,50&52,000
7.5 7.4 7.5 7.5 7.4
53,000-53,500 52,500-53,000 53,500-54,000 54,000-54,500 54,500-55,000
E 6:4 6.0 5.6
cm-’
10 11 12
1.0 1.4 0.8
13 14 15 16 17 18 19
0.5 0.5 0.5 0.5 0.5 0.3 0.3
TABLE 5. MEAN ABSDRPTION CROSS-SECTIONS OF THE O* HERZBERG~~NTIN~~M DEDUCEDFROMFDRMULA (1) kIteNd
FOR THE
r
CROSS-SECTION -_-
----
II
2-O BAND
300
1 e4m2
;
cni’) ~
----0
7
:
CONTINUUM-;7.53x (50500
1043
-
-___
LiBORATORY 50550
K
-
j
CALCU .ATION
-
50600
WRVENUMEER
51
50
51
JO
51
FIG. I(a).T~~TI~AL.ANDE~~ERI~TALAB~~BPTI~N CROSS-SECTIONSOFTHE ~-OSCHUMANP-RUNGE BAND OF o2 BETWEZN 50,500 AND 50,750 cm-’ AT 300 K. Oscillatorstrength and linewidth are 1.9 x 1Omsand 0.6 cm-‘, respectively. Strong effect of the Herzbcrg
continuum.
-24 1 50500
300
K
50550
50500
WAVENUMBER
‘C6”
50700
FIG. l(b). ABSORPTION STRUCTUREOF THE 2-O BAND WITHVARIATIONSOF f 10 AND k20% CROSS-SECTIONOFTHEUNDERLYINGCONTTNUUM AT 300 K.
50750
IN THE
‘0
FIG.
l(c). AEWRPTION
WITH ANDWITHOUTCONTINIJIJMBET~EEN SO,~OOAND 50,750m-' AT 270 K. Differences of a factor of IO between lines at 50,500 cm-‘. STRUCTURE
FIG. I(d). ALISORPTIONSTRUCTIJRE~IITHAND~ITIIOUTCONTIN~LMBET~EEN
50,500 AND 50,750cm 'AT 190 K. Increase of differences at high rotation levels; cross-sections reaching 3 x 1O-25cm* near 50,500 cn-‘.
CROSS-SECTION
4-O BAND P15 R17
:
:
P13 R15
PllR13
P7R9
P9Rll
P5Rj
P3R5
!A ~ R17 P15
Rl9
Pl7
:j
7-l
BAND
b.S.-3d5 L.w.-1.9cfd
----
: LABORAl ‘ORY
-
’ CALCULA TION
CONTlNUUM=f -23 51750
300 K
51800
5,850
(51750 WAVENUMBER
.40x l&4cm2
cd)
51900
FIG.~(~).THEORETICALANDEXPERIMENTALABSORPTIONCROSS-SECTIONSOFTHE~SCHUMANN-RUNGE BANDOF02BETWEEN 51,750 AND 52,000Cm-'AT 300K. Oscillator strength and linewidth are 2.7 x lo-’ and 3.6 cm-‘, respectively. Linewidths of 24 compared.
~~O-270-230-,905’~oo
51830
WRVENUWBER
51900
5,950
to be
5
FIG.2(b). TEMPERATUREEFFECTONTHEROTATIONALSTRUCT~REBETWEEN 51,750 AND 52,OOOcm-‘. Effects of a temperature decrease from 300 to 270,230 and 190 K on the 4-O and 7-l bands.
IO0
1046
CROSS-SECTION
-YE
-----
-
tA30RiT0~~
8-O BAND P13
/
’ CALCULATIOI I
:
Rl3Pl1,
RllP9
“”
R7Ps
I
13 Rl
is
r
9-O BAND R23
-19
P2l
II II
IP15
-21
k!
8-O BAND
O.Sd3.2~
16O
L.W.-2.lcni’ CONTIiJUUM-6.22x (54000 5qnon
300
K
FIG.3(a).THEORETICAL
2- 1 BAND
16*4cm2
AND
5cllUO EXPERIMENTAL
WAVENUMBER
51150
CROSS-SECTIONS OF THE 8-O SC--RUNGB 54.000AND 54.250cm-’ AT 300K.
ABSORPTION
BANDOFo,BlXlWBBN
!
t 54050 ~-270-230-190 K
1ti4
L.dV.-0.8cm’
cfli’)
54050
0.$.-2.8x
541ou
UAVENUtlBER
54150
54200
5
FIG.~(~).TMPBBATUICEEPPECTONTHEROTATIONALSTNJ~TUREBETWBBN 54,000A~~ 54,250~~'. Effects of a temperature decrease from 300 to 270,230 and 190 K particularly on the lines of the 12-1 and
13-l bands.
Aeronomic problems of oxygen photodissociationfigures (Figs 1a, 2a and
3a) make it possible to perform a detailed comparison at 300 K between the calculated and measured cross-sections. The calculations also make it possible to determine the respective role of the lines and of the continuum in the O2 absorption cross-section (Fig. lb) where variations of + 10 and f20% in the underlying continuum are depicted. Other figures have been published for temperature between 270 and 190 K (examples, Figs lc and Id) in order to define for each spectral interval the exact role
of the underlying continuum at varying temperatures adopted to atmospheric conditions. Finally, Figs 2b and 2c illustrate the variations in the structure of the absorption spectrum from the laboratory temperature 300 K to atmospheric temperatures 270,230 and 190 K. It is easy to follow, with decreasing temperature, the marked variations in the absorption of the rotation lines starting from the vibrational level u” = 1. The spectral interval 50,500-50,750 cm-’ (Table 6
TABLE 6. IDENTIFICA~ON OF O2 SHUMANN-RUNGE 50750 cm-’
5*:40 50522.3 50523. 50523.6 50527.4 50527. 50528.5 50530. 50530. 50531.3 50533.2 5053s. 50540. 50550 50571. 50571. 50572. 50573.2 50573. 50580. 50593. 50533. 50533.6 50597.2 50597.5 50538.2 50600 50607. 50607. 50607.3 50613.9 50614. 50614. 50637.3 50638. 50638. 50643. 50643.5 50644. 50650 50657. 50657.6 50658. 50661.6 50661.8 50662.5 50663.2
0
7 7 7
3 1 7 7 2 3 0 0 1
4 4
A
band
1973. 30 1373.29 1973.27 1373. 13 1979. 11 1373. 08 1978.33 1978.97 1378. 66 1378.66 1378. 63
5-l 5-l 5-l 5-l 5-l 5-l 2-O 2-O 2-O 2-O 2-O 2-O
P25 P25 P25 R27 R27 R27 P15 P15 P15 R17 R17 R17
1377.39 1977.39 1977.37 1977.10 1377. 1977. 1376. 1376. 1376.53 1376.39 1976. 1376.
2-o 2-o 2-o 2-O 2-O 2-O 5-l 5-l 5-l 5-l 5-l 5-1
P13 P13 P13 Rl!i R15 R15 P23 P23 P23 R25 R25 R25
2-O 2-o 2-o 2-O 2-O 2-O 2-O 2-o 2-o 2-O 2-O 2-O
Pll PI1 Pll R13 R13 R13 P 9 P 3 P 3 RI1 RI1 RI 1
5-1 5-l 5-l 5-l 5-l 5-l 2-O
P21 P21 P21 R23 R23 R23 P 7
1378.33
OS 07 56 55
38 35
1376.00 1975.99 1375.38 1375. 74
0 6 0 4 4 1
1975. 74 1975. 71 1374.81 1374.80 1974. 73 1374.53 1374.53 1974.57
6
1974. 04 1374.04
1
1374.02
1373. 88 1373.87 1373. 85 1973.82
1047
ROTATIONAL
50663.3 50663.6 50667. 50667. 50668.3 50683. 50683. 50683. 50686.8 50686. 50687. 50698. 50698. 50698.6 50700 50700.6 50700.6 50701. 50707.9 50703. 5070s. 50703. 50710.3 50712. 50712. 50716. 50716. 50717.2 50720. 50720.6 50721.2 50726. 50727. 50727.
band
A
”
7 7 3 4 7 8 3 1 3
1 1 3 7 5 6 7 7 4
3 I 3
1973. 1373.80 1373.64 1973.64 1373. 1373.04 1373. 1373.02 1972. 1372. 1972.88 1972. 1372. 1372. 1972.37 1972.36 1372.35 1372. 1972. 1372. 1972. 1971.36 1371. 1371. 1371. 1371. 1371. 1371.53 1971. 1971. 1971. 1371.33 1371.30
LINES 50500-
82
62 03 SO 30 46 45 44
08 03 03 01 SO SO 74 74 72 53 56 34
2-O 2-O 2-O 2-O 2-O 2-o 2-o 2-o 2-O 2-O 2-O 2-O 2-O 2-O
P P R R R P P P R R R P P P
7 7 3 3 9 5 5 5 7 7 7 3 3 3
2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 2-O 5-l 5-l 5-l 5-1 5-l 5-l 3-o 3-o 3-o
R 5 R 5 R 5 P 1 R 3 R 3 R 3 0 1 R 1 R 1 PlS PlS PlS R21 R21 R21 P23 P23 P29
M. NISI ET f?t d.
1048
and Figs la, b, c and d) corresponds mainly to the 20 band with an effect of the 51 band at 300 K. The experimental structure for absorption less than 2 x 1O-23cm* is due to laboratory noise. The effect of the underlying Herzberg continuum is important since it can be detected easily by the differences of + 10 and +20% illustrated in Fig. lb, particularly by the absolute values of the absorption cross-section with and without continuum at 270 and 190 K as depicted in Figs lc and Id.
The spectral interval 51,750-52,000 cm-’ is characterized by linewidths (Av = 3.6 cm-‘) of the rotational lines of the 4-O band (Table 7). These lines play a very important role in the overall pattern of absorption (Fig. 2a), since the effect of the Herzberg continuum is negligible and produces practically no variation when the absorption cross-section is varied by f 10 or +20%. The variation of the absorption cross-section with temperature (T = 300, 270, 230190 K) illustrates the decreasing role of the 7-l band
TABLE7. IDENTIFICATION 0~0~ SCHUMANWRUNGEROTATIONAL LINES 5175C 52000cm-’
7 9
51787.1 51787.4 51788.0 51796. 0 51796.3 51797. 0 51798.7 51798. 8 51799.3 51800 51825. 4 51825. 5 51826. 0 51829.3 51829. 5 51830.1 51850 51852. 7 51853. 0 51853.6 51855.0 51855.1 51855. 5 51862.6 51862.6 51863. 1 51865.9 51866. 1 51866. 7 51894. 3 51894.3 51894. 7 51897.1 51897.3 51897.8 51900 51903. 6 51903.8 51904. 3 51905.5 51905.6 51906. 0 51908.9
1931. 15 1931.
”
band
A 5*;50 51782. 51782. 51783.4
14
4-O 4-O
PI5 P15
4-o P15
1931.12 1930.98 1930.97 1930.95 1930.65 1930.64 1930.61 1930.55 1930. 55 1930.53
4-o R17 4-o R17 4-o R17 7-l R21 7-1 R21 7-l R21 7-1 P19 7-1 P19 7-l Pl9
1929.56 1929. 55 1929.54 1929. 41 1929.40 1929.38
4-O 4-O 4-O 4-O 4-O 4-O
P13 P13 P13 R15 R15 R15
1928. 54 1928. 53 1928.51 1928.46 1928.45 1928. 43 1928.17 1928.15 1928.05 1928. 04 1928. 02 1926.99 1926.99 1926. 98 1926.89 1926.88 1926.86
7-l 7-l 7-l 7-l 7-l 7-l 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O
R19 R19 R19 P17 P17 P17 PI1 Pll Pll RI3 R13 R13 P 9 P 9 P 9 Rll Rll Rll
1926.65 1926.64 1926. 62 1926.58 1926.57 1926. 56 1926. 45
7-l 7-l 7-l 7-l 7-l 7-l 5-O
RI 7 R17 R17 PI 5 P15 P15 P29
1929.17
51909.1 51909.
51911. 51911.9 51912. 51920. 51920.6 51920. 51922. 51923. 51923.5 51941.3 51941. 51941, 51943. 51943. 51943. 51948. 51948. 51949. 51950 51950.2 51950.3 51950.6 51956. 51956.6 51957.1 51957. 51957. 51958. 51966. 51967. 51967.2 51967. 51969. 51971. 51971. 51987.8 51987. 51988. 51989. 51989.
band
b
7
4 5 5 9 9 0
3 7 1 2 6 6 8 3
6
9 9 4 4 2 6 4 0 0 9 4 1 1
51989.5
51989. 7 51990. 4 51991.2
1926. 1926.
45 42
5-O 5-O
P29
7-l 7-l 7-l 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 4-O 7-l 7-l 7-l 7-l 7-l 7-1 8-l 8-1 8-l
P13 P13 P13 P 3 P 3 P 3 R 5 R 5 R 5 P 1 R 3 R 3 R 3 0 1 R 1 R 1 R13 R13 R13 Pll Pll Pi1 R29 R29 R29
P29 1926.36 8-l P29 1926.34 8-l P29 1926. 32 8-l P29 1926. 02 4-O P 7 1926. 02 4-O P 7 1926. 01 4-O P 7 1925. 93 4-O R 9 1925. 93 4-O R 9 1925. 91 4-O R 9 1925.25 4-o P 5 1925.25 4-O P 5 1925. 24 4-O P 5 1925. 18 4-O R 7 1925.18 4-O R 7 1925. 16 4-O R 7 1924. 98 7-l R15 1924. 97 7-l R15 1924. 96 7-l R15 1924.92 1924.92 1924. 90 1924. 68 1924.68 1924. 67 1924. 64 1924. 63 1924. 62 1924. 32 1924. 29 1924.29 1924.27 1924.21 1924. 15 1924. 15 1923. 53 1923. 52 1923.51 1923. 48 1923. 48 1923.47 1923. 46 1923. 43 1923. 40
1049
Aeronomic problems of oxygen photodissociation(Fig. 2b) and the change in the structure of the 4-O band at high rotational levels, PlSR17. In the 54,00&54,250 cm-’ interval, the principal contribution to the total absorption cross-section to the Pl-P13 lines of the 8-O band with an additional effect of the 12-1 and 13-1 bands (Fig. 3a). There is no contribution of the continuum (6 x 10mz4cm’) since the minimum cross-section is not less than 5 x lO_” cm2. The variation of the structure (Fig. 3b) is associated only with the rotational and vibrational populations related to temperatures 300-190 K, particularly in the 54,15@-54,250 cm-’ region corresponding to the lines of the (12-l), (13-1) and (14 1) bands. It seems, therefore, that there is a remarkable agreement between the experimental and theoretical crosssections. Yoshino et al. (1983) estimate that the error in the spectral range 60 to 12-O bands may vary from about 5% in regions of the principal absorption peaks to about 10% in window regions and that errors in the range of the absolute cross-sections below 1O-22 cm2 could be somewhat greater. In any case, our detailed modeling procedure in which the cross-sec2-o
6. THE SCHUMANN-RUNGE
BANDS AT 79 K
The recent experimental determination by Yoshino et al. (1987) of the cross-sections at 79 K with an instrumental bandwidth of 0.4 cm-’ has been compared with a theoretical calculation based on the spectroscopic parameters adopted at 300 K. We present our comparison in graphical format with a semilogarithmic plot for the 2-O bands through 12-O with a complete assignment of all rotation lines (Figs 4-14). According to Yoshino er al. (1987), their experimental values of the absolute absorption cross-sections would be of the order of 4% in regions of the principal absorption peaks while the errors in the range below 5 x 1O-22cm-’ should be greater (limited column den-
CROSS-SECTION T
-20 r
Rl7
j
R5 P13
P25 -21
tion is computed as a function of wavenumber for lines with Voigt profiles and in which predissociation line widths are treated as parameters produces excellent agreement with the best experimental data independent of the instrumental width. It is also justified by a comparison of the theoretical and experimental cross-sections at 79 K.
;pll
. . . . . . .. LABORATORY
WARVAkD)
e
BFNJSS$LS)
CALCUiATION
Rl’Ij
/ RI3
P9
R9
P7
R7
P5
h
3 -23
-24 50
3
79 K
50550
50600
URVENUIlBER
50650
50700
24 BAND AT 19K. less than 5 x 1O-23 cm’ in the laboratory noise. Agreement and experimental peaks.
50750
FIG.~.AENRFTIONCROSS-SECTIONSOFTHE
Experimental
cross-sections
between theoretical
3-o
51150
79
CROSS-SECTIPI
K
59200
51250
URVENUHBER
51 JO0
5,350
FIG.% ~sORFT~ONCROSS-SECTIONSOPTHE ~~BANDAT~~ K. Rotation linesof ‘60’80 isotope with spikesfor cross-sectionsnot lessthan 5 x IO-” cmz.
5,750
79
5,800 K
51850
WRVENWIBER
5,900
FIG. 6. ABWRPTION c~oss-_swr~o~OFTHB4-O BAND AT79 K. Linewidthdeterminedat 300K in agreementwith structureat 79 K.
5
00
5-o
1051
CROSS-SECTION
-19
-20
;;
0 fu-21 Tii
3 -22
-2: 5:
10
79
52450
K
WAVENUMBER
52500
FIG.~.AJSORPTION CROSS-sEcnoNSOl'THE~BANDAT79K. Underlying continuum (0.7 x 1O-23 cm*) without any effect.
..f....
_-20
LAyRAT0RY. 1 CAijCULAiloN j :
8 z
I !
:
/ :
-‘CON-iINUlJM_7ix 162%m2
6 ;_
R
,!
-22
x
“0
%’
LINES
“A#.-
I.Pa
; iW.-l&m^l
I”
i I
FIG.~.AWXPTIONCROSS-SECTIONSOFTHE~~BANDAT~~K. Spikes corresponding to ‘60’80 lines clearly apparent between 160, lines below the “O”O
head.
7-o
CROSS-SECTION --
j-..
__ -Ftn
.P9
.22
-23 5:
I= 5o
79
1:
-iFI9 i. !P7
fi7-: ..P5.
‘R5 $?2Rl _._j _
j O.Sr34x1(
53500
53550
K
53600
I :
jS.1
”
i L.W,-l.Qcm”
-: : ._
i
i
-/
/
53650
-I
I 53700
WRVENUIIBER
FIG. 9. ABSORPTIONCROSS-SECTTIONSOFTHEI 7-O BAND
Laboratory noise still noticeable near lo-”
.23 5: '
54000
79
K
54050
54100 URVENUHBER
AT 79K. cm’.
54150
5
COO
~G.lo.~~~ON CR~-~~ONSOF~8~B~AT79 K. Apparent anomaly between P13 and Pt5 lines as a result of the laboratory limited cohmm density.
9-o iii
1053
CROSS-SECTtal
-1s
R15 I P13
Pl5
Ril i RQ PQ 1
R13 iPl1
R7’ /R5. R$Rl P5 ! kP3.A
-19
_ -20 8
z f ;;
18~
-22
!‘80
-3 0
79
54450
K
FIG.
54500
11. ABSORPTION
LINES
:
* L .W.==l .acti’
i 1
59550
WAVENUHBER
CROSS-SEC~ONS
:; CL%-l.0xld5
0F THE 9-O BAND
AT
79 K.
Superposition between P13 and R13 lines of 160”0 spikes and laboratory noise, >S x lo-” < 1O-22cm’, respectively. 10-O
54
54600
cm* and
CROSS-SECTION
-1s
-23 54010
79
K
54850
FIG. 12.ABSORPTION
59950 WAVENUt-lBER CRW-SECTIONS
OF THE 1fM
55000
BAND AT
55050
79 K.
All aspects described in Figs 4-10 present in a comparison of theoretical and experimental structures.
1054
11-O
m7
..: P15
-22 55200 79
K
.I
ms_
55250
.:. :. P13.
55300
WRVENUIIBER
55350
55400
FIG. 13. ABWRPTION CR~SXIXTIONS OFTHE1IHI BANDAT 79 K. Remarkable differences in structure above and below ‘60’*0 head. 12-o
CROSS-SECTlaJ
-17
-18
_-1s 8
z f s
q-20
-21
-22 55
FIG. 14. ABWRPTIONCROSS-SECTIONS OFTHE12-O BAND Last band with experimental cross-sections.
AT
79K.
1055
Aeronomic problems of oxygen phot~issociation-~~ 54000-54250Cm-’
TABLE%IDENTIFICATTONOF02S CHUMANN-RUNGEROTATIONALLINES
5dhw 54000.0
54000.2 51000.5 54003. 54004. 5dOO5.4 51006. 54005. 54035. 54036.4 54036. 54437. 54035. 54039. 51040. 5dOdO. 54040.9 5##41,2 54044. 54050 54051.2 54054.4 54456. 54456. 54057.2 54057. 54062. 54063.2 54063. 51071. 54072. 54072. 54075.5 54075.6 54075. 54078.2 54075. 54479. 54084.9 51086. 54087.3 54087. 54088. 54050. 54090.6 54092.0
7 e 9 6 9 6 0 0 4 0 a
0
0 5 5 6 7 5 0 3
9 7 0 Q a 0 6
band
1 1551.55 1553.55 155I.54 3553. 73 1553. 65 1551.67 3553.62 1551. 56 3550. 62 3550.61 3550. 60 1550.59 3550.55 1550.50 1550.45 1560.45 3550.45 1a5v. 44 1550. 34
6-V 5-V a-o 12-f 32-f 12-f 33-f 33-I id-1 a-o a-a 8-O fz-I 12-f 12-3 5-V 34-f a-v 14-l
PI3 P33 P?3 P35 PI5 PI5 f23 P23 P27 R33 Rf3 a13 a35 R15 a15 PI? P27 Plf P27
1550. 1549.
13-l 13-l 32-i 13-1 32-3 12-f S-O S-O S-O a-o 5-o 5-V B-O 5-O 3-O 9-V 9-O S-O
R23 R23 P13 R23 P33 P?3 W7 RZ7 R27 a11 RI? Rt? P 9 P 9 P 9 p25 P25 P25
30 99 1649. 93 1549. 92 3549.59 1a49.5a 1549. 71 1849. 69 fa49. 67 I549.39 1349.39 1549.38 lads. 27 1849.26 1549.25 1519. 37 1849.16 lad9. 35 ia45.95 Iada. 93 1548.56 1545.55 1548. 54 1545. 75 1545. 75 fada. 70
ld-1 R/7
12-l 12-f 12-f 13-f 14-l 33-l 33-f
R33 R33 a13 P21 ff27 F23 PZ?
54092. 54094. 54100 54100. 54101. 54141. 5df VI. 54101. 54102. 5dl02. 54104. 54104. 54104. 51324. 54324. 54124. 54126. 54326. 54326. 54127. 54125.2 54328. 54131. 54134. 54336. 54135. 54139. 54139.9 54140. 54341. 54141.4 54141. 54141. 54142. 54143. 54143. 54113. 54144.3 54144.4 54144. 54147. 54147. 54150 54152. 54152. 54152.
band
1
”
9 3
1645.67 15-l 3648. 62 14-3
8 f 3 d 6 6 7 0 f 4 3 d 7 5 6 9 0
1546.40 1545.39 3545.33 3545.38 1545.35 1548.34 l545.34 f&IS. 29 1845.29 1545.25 1547. 60 1547.59 1547.55 1547. 52 1547. 52 1647.51 1547. 51 f547. 47 3547. 45 1547.35 1847.26 1547.20 1847. ?I 1547.07 1547. 07 3547. 03 1547.03
6 5 d 1 6 5 9 0
15-3 5-o a-o f2-I 5-V 12-I 12-f 8-V B-O 5-O 5-V 5-V a-o 5-V a-0 5-o 12-1 32-I 12-f 13-I 13-f 33-I 15-f
P29 R27 P29 R 9 R 9
Pff
32-l 12-i
R 9 PI1 PI1 P 7 P 7 P 7 R 7 R 7 R 7 P 5 p 5 P 5 Rl? RI? RI1 R23 RZ3 R21 a29 P25 P 9 P e
12-l
P 9
14-l
t5dz
0.2 8-o a
01 00 96 96 94 ed
4
3547. 1547. 1516. 1546. 1546. fad6. 1546.92 Ii346. 3546.eV 1546.52 1516.
4 5 9
5 8 9 V 5 7
7
f
Bf
8-O 5-O 5-O 8-O 5-O 9-V 9-V 34-3 s-o 14-3 15-l
5 R 5 R 5 P 3 P 3 P 3 a25 a26 P25 a25 P25 a29
1546. 64 1546. 64 1546.62
5-V 5-V 5-V
R 3 R 3 R 3
sity). This is the explanation of the strong noise (loga~~c scale) in the figures ~o~es~on~ng to 2-O and 3-O where the continuum cross-section is less than 5 x 10-23 cm2. Spikes which are clearly apparent in the experimental data, from the 6-O to 12-O bands, between the principal lines shown with their assignments are mostly rotational lines of the isotopic molecules ‘60*80. These spectral features are shown in the vari-
91
”
1
54353. 3 I546. 62 1546. 62 54153.1 54155. a 1546. 52 543 57.2 1546. 45 54157. 4 1546. 47 54155. 0 1546. 45 lad& 44 54355.4 54158. I 1546. 43 54363. 3 1846.35 54362.1 1546.31 54162. 4 1546. 30 54164. 6 1546. 22 54167. 0 1846.14 54165. 1 3546. IV 54171. 5 1545. es 54372. 4 1845. 96 64172. 5 1545. 96 54355.5 1545. 50 51155.2 1545. 42 54159.2 1545. 39 54159.4 1545.38 54190. 9 3545. 33 541.94. f 3545.22 54196. I 3545.15 54197. 0 3545. 32 54197. I 1545. I2 54200 54204.2 1544. 55 54206. 9 1544. 79 54205. 4 15dd. 73 54205. 4 ISdd. 73 54209. 3 1844.70 54209. 5 1544.70 54210. 7 3844. 65 54213. 5 1544.55 5121d. 7 1544.52 54215.2 1544.50 5dZI7. 5 I5dd.42 51217. 9 IBId. 41 54215.4 1844. 39 54239. V fadd. 37 54219. 4 f544. 36 54221. 6 15dd.25 54222.2 2541.26 54222. 5 1844.25 51222.5 I5dd. 24
band
5-O 15-f 5-O 5-O 5-O 9-O 9-V 3-O 12-Z 32-f 12-3 33-3 13-l 13-1 12-l 32-l 32-i 14-f 12-l 12-1 12-f 14-3 14-l 32-l 32-l 12-1
P I R29 V 1 R 1 R 1 P23 P23 P23 R 9 R 9 R 9 PI9 P19 P?9 P 7 P 7 P 7 R25 R 7 R 7 R 7 R25 R25 P 5 P 5 P 5
13-I 13-l t3-1 12-f 1.2-f 12-f 15-3 12-l 12-l 12-f 16-l f5-I S-V S-V 3-O 32-f 15-I 12-I 12-f
RlS RI9 /??9 R 5 R 5 a 5 f’27 P 3 P 3 P 3 P29 P27 R23 R23 R23 R 3 I’27 a 3 R 3
ous figures with an indication of the heads of the %‘*O bands. We have verified our assigmnents thanks to unpublished data (Yoshino-Egmont, personal communication). As an example, the crosssections of the 8-O bands of 160, and ‘60’80 are compared in Fig. 15. It is clear that the four spikes (see Fig. 10) in the window between the P9 and Pl 1 lines of 1602near 54,050 cm-’ correspond to tire first lines of the r60’80 molecules and that the two groups
1056
CROSS-SECTION
-22
/
-23 53950 79
I
54000
K
54050
I
I! WAVENUtlBER
541p
ds150
54200
FIG. 15. ALSORPTION CROSS-SECTIONS OF THE 160, AND‘60’80 BANDS AT 79 K. Comparison between ‘6O’8Oexperimental and 1602theoretical determinations. 300 K
CROSS-SECTION
R17 1 P15 I
150 0
79
K
50550
R15 P13
j R13 i .Pll
50600
2-o
Ril i P9 /
WAVENUMBER
50650
R9 P7
R7 -d5 R3Rl P5 P$ p1
50700
-- --
5
‘50
FIG. 16. ROTATIONAL STRUCTURES OFTHE2-O BAND AT 300 AND 79 K. At high rotational levels, upper curve for 300 K and lower curve for 79 K. At P7-R9 lines, beginning of an inverted position for both curves.
1057
Aeronomic problems of oxygen photodissociation-
R17 i ---
0
79
K
R,5 --‘i
51800
51850
Fill
R13
WAVENUMBER
51900
R9
R7i
51950
R5-R3Rl
1
52000
FIG. 17. ROTATIONAL STRUCTURES OFTHE40 BANDAT 300 AND79 K. At high rotational levels, upper curve for 300 K and lower curve for 79 K. At P7-R9 lines, beginning of an inverted position for both curves.
with a double structure between the Pl 1 and P13 lines of ‘“02 near 54,025 cn-’ belong to the 160180 isotopic molecule.
7. COMPABIBON BETWEEN THE
ARSORPTION
STRUCTURES AT 300 AND 79 K
The theoretical cross-sections of the (2-O) to (120) bands at 300 and 79 K have been compared. Two examples are shown in Figs 16 and 17 for the 2-O and 4-O bands. Details of the line assignments (Yoshino ef al., 1984; Nicolet et al., 1987) show (see Figs la and 2a, respectively) that the main apparent differences are due to the temperature contrast, specifically the disappearance of the lines corresponding to u” = 1 and the decrease of the intensity of the line corresponding to a” = 0 at relatively high rotational levels (see Tables 6 and 7). This means that the absorption cross-sections at 79 K as shown in Figs 4-14 are practically free from any lines of other bands, and they increase on the lower rotational levels.
8. CONCLUDING REMARK The high resolution absorption cross-section measurements made by the Harvard-Smithsonian group at 300 and 79 K of various bands of the Schumann-Runge system of O2 have allowed the calculation of linewidths of rotational lines for which the band oscillator strengths were obtained. An accurate calculation of the band structures at various atmospheric temperatures may be performed when adequate averaged linewidths are determined for each band.
Acknowledgements-This work is based not only on the most recent publications available, but also on unpublished experimental data. Our special thanks go to the members of the Harvard-Smithsonian Croup who have kindly provided such data. Support for the preparation of this work has been facilitated by grants from the Commission of the European Communities, Directorate-General for Science, Research and Development, Environment Research Programme, of the Office of Naval Research contract NOO14-86-K-0265WOO2 with the Communications and Space Sciences Laboratory of Penn State University, and of the Chemical Manufacturers Association Contract FC 85-563 with the Institut d’Abronomie Spatiale.
M. NICOLETet al.
1058 REFERENCES
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Brix, P. and Herzberg, G. (1954) Fine structure of the Schumann-Runge bands near the convergence limit and the dissociation energy of oxygen molecule. Can. J. Phys. 32, 110. Cheung, A. S.-C., Yoshino, K., Parkinson, W. H. and Freeman, D. E. (1984) Herzberg continuum cross section of oxygen in the wavelength region 193.5-204.0 mn and band oscillator strength of the (O-O) and (la) SchumannRunge bands. Can. J. Phys. 62, 1752. Cheung, A. S.-C., Yoshino, K., Parkinson, W. H. and Freeman, D. E. (1986) Molecular spectroscopic constants of O@;), the upper state of the Schumann-Runge bands. J. molec. Spectrosc.
119, 1.
Fang, T. M., Wofsy, S. C. and Dalgamo, A. (1974) Opacity distribution functions and absorption in SchumannRunge bands of molecular oxygen. Planet. Space Sci. 22, 413. Lewis, B. R., Berzins, L. and Carver, J. H. (1986a) Oscillator strengths for the Schumann-Runge bands of 1602. J. Quant. Spectrosc. Rad. Trans. 36,209. Lewis, B. R., Berzins, L., Carver, J. H. and Gibson, S. T.
(1985a) Decomposition of the photoabsorption continuum underlying the Schumann-Runge bands of %-
I. Role of the B3Z state. I-A
new dissociation limit. J. Quant. Spectrosc. Rad. Trans. 33,627. Lewis, B. R., Berzins, L., Carver, J. H. and Gibson, S. T. (1986b) Rotational variation of predissociation linewidth in the Schumann-Runge bands of 1602 J. Quunt. Spectrosc. Rad. Trans. 36, 187. Lewis, B. R., Berzins, L., Carver, J. H., Gibson, S. T. and McCoy, D. G. (1985b) Decomposition of the photoabsorption con&u& underlying the SchumannRunae bands of ‘6O,-II. Role of the 1% state and collision induced absorption. J. Quant. Spectrosc. Rad. Trans. 34,405.
Nicolet, M., Cieslik, S. and Kennes, R. (1987) Rotational structure and absorption cross sections from 300 K to 190 K of the Schumann-Runge bands of OZ. Aeronomica Acta, Brussels. A, no. 318, I-340. Nicolet, M. and Kennes, R. (1986) Aeronomic problems of the molecular oxygen photodissociation-I. The 0, Herzberg continuum. Plunet. Space Sci. 34, 1043. Nicolet, M. and Kennes, R. (1988) Aeronomic problems of molecular oxygen photo-dissociation-IV. The various parameters for the Herzberg continuum. Planet. Space Sci. 36, 1069.
Yoshino, K., Freeman, D. E., Esmond, J. R. and Parkinson W. H. (1983) High resolution absorption cross section measurements and band oscillator strengths of the (1, Ok (12,O) Schumann-Runge bands of Or. Plunet. Space Sci. 31, 339. Yoshino, K., Freeman, D. E., Esmond, J. R. and Parkinson, W. H. (1987) High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge bands of oxygen at 79 K. Planet. Space Sci. 35.1067. Yoshino, K., F&man, D. E. and Parkinson, W: H. (1984) Atlas of the Schumann-Runge absorption bands of O2 in the wavelength region 175-205 nm. J. phys. Chem. Ref. Data 13,207.