Laboratory spectra of CCL2F2 in the 10.8 micron region was recorded, using a tuneable diode laser spectrometer. Effects of air-broadening at pressures up to 48 Torr show that spectral structure should be exhibited under high resolution at altitudes as low as 19 Km. The single line, pressure-broadening coefficient for CCL2F2 was estimated to be 8 MHz/Torr FWHM

Jennings, D. E.

English

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Technical Memorandum 7,9n41
(NASA-T`1-7AC 41 )	 DIODE LASER SPEcI RA. OF
CC12F2 "LEAF I C.c FUN M:	 AIR-EROADENING
E'FFEC'TS (NASA)	 13 p 6C A02/11E y01	 CSCL 20E Unclas
-,3/36 02498
Diode Laser Spectra
of CC1 2 F2
 Near 10.8 pm
Air-Broadening Effects
D. E. Jenrings I
NOV r,MBER 1977 	 SZ,93 ^^^
LP
National Aeronautics and
Space Administration	 Q^	 <
Goddard Space Flight Center 	 ^r^91 ^^ tiL ^Greenbelt Maryland 20771
N78-16355
DIODE LACER :;PECTRA OF CC121"2
NEAR 10.85 Lm; AIR-BROADETFING EFFECTS
D.E. Jennings
NA; A/Go ddard "pace F11.ght Center
Greenbelt, Maryland 20771
ABSTRACT
Laboratory spectra of CC12F2 in the 10.8µm region has been
recorded using*, a tuneable diode laser spectrometer. Effects of air-
broadening at pressures up to 48 Torr show that spectral structure
should be exhibited under high resolutiwu --t altitudes as low as
19 Km. The single-line pressure-broadening coefficient for CC12F2
is estimated to be 8 IyUfz/Torr FWHM.
Stratospheric dichlorodifluoromethane is of increasing interest
because of its possible role in the ozone-depletion chemistry of the
upper atmosphere (Clyne, 1974; Molina and P.owland, 1+'(4; Cicerone
et al. 1 1974). It is important in this context to have a krnowledge
of the altitude profile of the CC12 F'2
 mixing ratio, and this can be
<)btained experimer:tally either from insitu measurements (^chrneltekopf
et al. 1976) or from inversion of high-resolution atmospheric spectra.
The second technique lends itself well to ground-ba.,ed monitoring,
but requires some knowledge of the behavior of the spectra under
conditions of pressure .tnd temperature similar to those in the
stratosphere. Becentl_y, CC1,)F has been detected in solar absorption
with balloon-borne (Williams et al., 1976) and ground-based (Bradford
et al., 1976) spectrometers. Goldman et al., (1976) have reported
laboratory spectra of the 10.8Lm band of CC1^F^ obtained at moderate
resolution 10.06 cm 1 ).	 y
With the introduction of infrared laser heterodyning as a remote
sensing technique (see, for example, McElroy, 1972, Peyton et al.,
1 r'('(, and Mwnma et al. , 1 i'('O , it has bec o me possible to obtain ultra-
high resolutloti (10 4 cm 1 ) atmospheric spectra. Carbon dioxide
lasers used as local oscillatcrs provide coverage of several discrete
segments, each about 0.1 cm 1 wide, it: the 10.8µm band of CC12F2.
Tunable diode lasers, which are a , rril:ar.le with output powers approaching
the required )..tvel for sn ,)t-noise limited heterodyning (Murnna et al.,
1)(5a and b, Ku acid. '.;pears, 1977), provide --overage at any wavelength
1
in this region in se, ,7nents up to several wavenurnbers wide.
In anticipation of the teed for ultra-high resolution laboratory
data in the interpretation of stratospheric spectra, a tunable diode
laser spectrometer has beer, used to record the regions near X2.8 cm-1
and Q1.( cm 1 in the vibration-rotation spectrum of CC1 2F2 . Thee
are the strongest absorption regions in the 10.8µm band, and correspond
to the q-branches of V  (Plyler and Benedict, 1:51) for the C35C12F2
and C35Clj(Cl 2 isotopic species, respectively.
The aample was taken from a standard commercial cylinder and was
not isotopically purified. A pressure of 0.200 Torr CC1 2F2 was placed
in a 30 crn length cell at ambient temperature (25°C) and air was introduced
into the cell to achieve the desired partial pressures. Gas pressure
in the sample cell was measured with a 0-1000 Torr MKS type 1'(0 Baratron
pressure meter. Wavenumber calibration of the spectra was established
using a germanium F'abry-Perot etalon and till  lines of known "requency.
The c.".ects of air-broadening on the C2.8 cr y-1 °pPctra are shown
in Figure 1. In this region, as in all portions of tl;e % band,
the line density is so great that single-line analysis is impossible.
The structure exhibits good intensity contrast, however, at pressures
corresponding to altitudes in the upper atmosphere.
.Ln particular, this is true of the )22.9 to )P_2.7 cm 1 portion
of the spectra, where i1he absorption "eatures !which are each due to
more than one transition) are especially prominent and regularly
spaced. This spacing, 0.01 1+ em 1 ( 1+08 1411z) , is wide enough to retain
spectral stru .-cure at atmospheric pressures as high as 1+8 Torr, or
2
altitudes as low as 19 Km. The apparent broadening in this region, as
measured from the full width at the absorption level hallway between
minimurn and maximum absorption for each feature, is 2 Miz/Torr. The
single-line broadening coefficient for CC1 2 F2 can be estimated form
this spectra to be pv = 8 MHz/Torr FhlN.
It should be noted, for the purpose of heterodyne monitoring
using a CO2 laser local oscillator, that the P(42) transition of the
10.4^,m lasing band of 12 C 1602 occurs near this region at )22.914? cm-
Also, the R(12) line of 13C 1602 occurs at X3.1114 cm 1 , near the branch
head.
The structure near the branch head -1(923.2 cm ) is the most
recognizable series anywhere in the spectrum. A second Q-branch
head. probably corresponding to the v^ + .ja - v2 hot band (Gnldrnan
et al. 1976) appears at ')22.7 cm-1
 . A more complete analysis of the
v6 band will be the subject of a later paper.
The air-broadening ef'f'ects in the 921.7 cm 1 region are shown
in Figure 2. Although Some high-resolution structure is discerni.bL:.
at pressures as high as 24 Torr (altitudes as low as 23 km), the
intensity contrast here is not as pronounced as in the Q2.8 crrl -
 1
region and is riot expected to be as useful in the analysis of stratospheric
spectra.
The CO2
 loser heterodyne spectrometer which is coupled to the
48-inch telescope at the Goddard apace Flight Center (Mumma et al. ,l)77)
has been used to record ground-based solar absorption spectra of the
10.8 µm band of CC12 F2 , and the work reported here was instigated
r
3
as pert of that program. The heterodyne observations are presently being
completed in that region, and results will be reported later.
Acknowledgements. The author wishes to thank Dr. J. J. Stillman for
collaboration in building the diode spectrometer and Mr. J. L. Faris for
laboratory assistance, and also to express appreciation to Dr. M. J. Mumma
for suggestions and encouraf;ement.
Ift I
4
r
References
Bradford, C.M., F.H. Murcray, J.W. Van Allen, J.N. Brooks, U.G. Murcray
and A. Goldman, Ground level detection and feasibility for monitoring
of several trace atmospheric constituents by high resolution
infrared spectroscopy. Geophys. lies. Levt.,3, 387, 1976.
Cicerone, R.J., R.S. Stolarski and S. Walters, Stratospheric ozone
destruction by man-made chlorofluoromethanes. Science, 185,
1165, 1a74.
Clyne, M.A.A., Destruction of atmo3pheric ozone, Nature, 24 , 796, 1974.
Goldman, A., F.S. Bonomo and D.'-.. Murcray, Statistical-band-model
analysis and integrated intensity fur the 10.8µm band of CF2C12.
(eoj!t s . lies. Lett., 3, 30), 1976. 
Ku, R.T. and D.L. Spears, High-sensitivity heterodyne radiometer using
a tunable diode laser local oscillator. M.T.T. Lincoln Laboratory
°,olid :;hate Research ouarterly Technical "mmiary Report, p.l, 29 April,
1) l7.
McElroy, J.H., Infrared heterodyne solar radiometry. 	 ^^pt., .11,
1619, 1972. 
Molina, M.J., and F.S.L. Rowland, Stratospheric sink for chlorofluoro-
methanes:Chlorine atom-catalysed destruction of ozone. Mature,
249, Oslo, 1974.
M»am , M.J., T. Kostiuk, S. Cohen, D. Muhl, and Y.C. von Thuna,
Infrared heterodyne spectroscopy of astronomical and laboratory
sources at 8.5µm. Nature, 253, 514, 1975a.
Mumma, M.J., I. Kv,tiuk, S. (:Wien, D. Buhl, and P.C. von Thuna,
Heterodyne spectroscopy of astronomical and laboratory sources
at 8.5µm using, diode laser local oscillators. Space Sci. Rev.
1`1, 661, 1975b.
:dumma, b;.J. , T. Kostiuk, and D. Bulil, A 10µm laser heterodyne spectrometer
for remote detet:tion of trace gases. To be published, Opt. Eng.
Peyton, B.J., R.A. Lange, M.C. :,avage, R.K. Seals, and F. Allario,
Infrared heterodyne spectrometer meajurement-s of vertical profile
of tropospheric amr,;onia and ozone. A1AA Conference, Los Angeles,
California, January 1377.
Plyler, E.K., and W.S. Benedict, Infrared spectra of eighteen halogen-
substituted methanes. J. Res. N.B.S., 4`j, 202, 1951.
Scluneltekop", A.L. , P.D. Goldan . W.J.  Harrop, T.L. Thompson, D.L.
Albritton, M. MacFarland, A.E. Sapp, and W.R. I{endersoi,,
Balloon-bor,-ie stratospheric graL--rumpling system. Rev. Sci
Instrum., 41, 147_;, 1976.
iliams, W.J., J.J. Kusters, A. Gol(bnan and D.G. Murcray, Measurements
of stratospheric halocarbon distributions using infrared techniques.
Ge^phys. Res. Lett., ^, 379, 1`)7(-).
U.Standard Atmosphere, 1976, p.50, document DJOAA-S/T 76-1562, U.S.
Goverpment Printing Office. 'r'ashington, D.C.
F'I(iUc3 :APTION5
Fie. 1 laboratory air-broadened spectra of CC1,21-2 near '122.8 cm-1 I
The 30 cm sample cell was filled to 0.200 Torr CC1 2 F2 (top
trace) and air was then introduced to reach the partial
pressures indicated. Temperature = 250C. Altitudes are
according to U.S. Standard Atmosphere, 1)76.	 Note that
the ordinate is linear in diode current and therefore slightly
non-linear in frequency.
Fig. 2 Laboratory air-broadened spectra of CC1 2 F2 near 321.7 cm-1.
Remarks in the caption to a'igure 1 apply here also. Note that
the range of the frequency scale is less than in i1gure 1.
w0
f--
cn
z
W 0
F--z
W
Q
J
W
0
0
AIR-BROADENED
CC 1 2 F`
6;,
I
	
I	 I	 ^	 ^	 I	 I	 ^ I,
.
+^	 ^r I I I ^111 111) ^^	 ^	 ^	 ^) (	 ^	 ^	 I	 ^,
923.2	 9230	 9228
	 922.6	 922.4
FREQUENCY (cm-1)
AIR -BROADENED
J
M1
l ^	 1
^1	 1
f'^	 d	 M
V	 3 TORR
37Km	 +rwr ^
v^	 CC12 F2
-MI
t r^
^M
l
r
I
^
`M
Y
,
, ^	 33 Kr"
12 TO R R	 Y
22 Km
U
24 TORR
23 Km	 Ohl
^	 hr.
48 TORR
19 R m
921.9	 921.8	 921.7	 921.6	 921.5
FREQUENCY (cm -I )
W
Z
Lli
aJW
Lr
-)ber 17, 1977
	
l.' TAumENT B
BIBLIOGRAPHIC DATA SHEET
1. f(e purt No
_
2	 Government Accession No. 3.	 Recipient's (.ataioy No.
4. Title and Subtitle S. Report Date
Diode I.a.;er Spectra of CC].2 F	 !tear
10.8µm. Air-br , )adening eftecis 6. Performing OrgdnizationCode
7, Author(j) 8. Performing Organization Report No.
D.E.	 •Jcnni.ngs
9. Performing Organization Name and Address 10. Work Unit Nu.
Infrared & Radio Astronjltly Branch
11. Contractor Grant No.Laboratory for Extraterrestrial Physics
NASA/Goddard Space Flight Center Y
13. Tyne o! Report and Period Covered';t'eenbelt,	 ''a) 20'('(1
12. Spon-ring Agency Name and Address
r
14. Sponsoring Agency Code
15. Supplementary Notes
16. Abstract
Laboratory spectra of CC12F2 in tile 10.6µ1u region has
been recorded using a tuneable diode laser spectrometer.
Effects oF' air-broadening at pressures up to 48 Torr show that
spectral structure should be exhibited under high resolution
at altitudes as low us 1') Km.	 'ihe single-line pressure-
br-)udening coefficient for CCIpF2 is eotimated to be 8 MHz
Torr F1 11M.
11. Key Words (Sciccted by Author (s))
	 --T18. Distribution Statement
10. Security C'.5srf. (uf this report)	 120. Security Classrf. (of this p aqe)	 21.	 No. of Pages	 22. Pric-e
r	 I 	 t r ,, r..,I	 • iI	 t I,	 ,,	 . 1,,	 6,1. Yug,mn 2 .1151	 q,^, 1 <r•..


Diode laser spectra of CCl2F2 near 10.8 muon M: Air-broadening effects

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