Infrared measurements of atmospheric CH
3
CN
Armin Kleinbo
̈hl, Geoffrey C. Toon, Bhaswar Sen, and Jean-Franc
̧ois L. Blavier
Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
Debra K. Weisenstein
Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA
Paul O. Wennberg
California Institute of Technology, Pasadena, California, USA
Received 2 August 2005; revised 6 September 2005; accepted 20 September 2005; published 6 December 2005.
[
1
] For the first time CH
3
CN has been measured in the
Earth’s atmosphere by means of infrared remote sensing.
Vertical profiles of volume mixing ratio were retrieved from
12 solar occultation measurements by the balloon-borne
JPL MkIV interferometer between 1993 and 2004. Profile
retrieval is possible in an altitude range between 12 and
30 km with a precision of
20 ppt in the Arctic and
30 ppt
at mid-latitudes. The retrieved CH
3
CN profiles show
mixing ratios of 100–150 ppt a few kilometers above the
tropopause that decrease to values below 40 ppt at altitudes
between 22 and 30 km. The CH
3
CN mixing ratios show a
reasonably compact correlation with the stratospheric
tracers CH
3
Cl and CH
4
. The CH
3
CN altitude profiles and
tracer correlations are well reproduced by a 2-dimensional
model, suggesting that CH
3
CN is long-lived in the lower
stratosphere and that previously-proposed ion-molecule
reactions do not play a major role as loss processes of
CH
3
CN.
Citation:
Kleinbo
̈ hl, A., G. C. Toon, B. Sen, J.-F. L.
Blavier, D. K. Weisenstein, and P. O. Wennberg (2005), Infrared
measurements of atmospheric CH
3
CN,
Geophys. Res. Lett.
,
32
,
L23807, doi:10.1029/2005GL024283.
1. Introduction
[
2
]CH
3
CN (methyl cyanide or acetonitrile) is a long-
lived trace gas in the Earth’s atmosphere. It is mainly
produced in the troposphere by biomass burning. Tropo-
spheric values typically range from about 50 to 150 ppt
[
Hamm and Warneck
, 1990;
Singh et al.
, 2003], although
values can be considerably higher in localized areas, e.g. in
the outflow of forest fires [
Livesey et al.
, 2004]. A major
sink for CH
3
CN is wet removal in the troposphere and
deposition in the ocean [
Hamm et al.
, 1984;
Singh et al.
,
2003]. Chemical loss of CH
3
CN is primarily caused by the
reaction with OH, although there are still uncertainties about
the products of this reaction [
Tyndall et al.
, 2001]. Reac-
tions with O(
1
D) and O(
3
P) can also play a role at
stratospheric and mesospheric altitudes [
Arjis and Brasseur
,
1986].
[
3
] First indications of the presence of CH
3
CN in the free
atmosphere were derived from balloon-borne positive ion
composition measurements using mass spectrometry
[
Arnold et al.
, 1978]. This was the favored method used
in several subsequent in-situ studies of CH
3
CN [e.g.,
Knop
and Arnold
, 1987;
Schneider et al.
, 1997], although more
recently in-situ measurements have been performed using
gas chromatography [
Singh et al.
, 2003]. Atmospheric
CH
3
CN has been measured remotely from space in the
microwave region by the Microwave Limb Sounder (MLS)
[
Livesey et al.
, 2001, 2004]. In the infrared wavelength
region only an upper limit has been reported so far from the
analysis of ground-based solar absorption spectra [
Muller
,
1985].
[
4
] Here we report the first infrared measurements of
atmospheric CH
3
CN. Our analysis uses balloon-borne solar
occultation measurements by the Jet Propulsion Laboratory
(JPL) MkIV interferometer [
Toon
, 1991] between 1993 and
2004. We demonstrate the capability to retrieve vertical
profiles of CH
3
CN in the lower and middle stratosphere,
compare the results to previous measurements and 2D-
model calculations, and interpret them in the context of
atmospheric conditions.
2. Spectroscopic Database for CH
3
CN
[
5
] Until recently the availability of infrared cross-sec-
tions for CH
3
CN was limited to data with low spectral
resolution obtained at room temperature. Spectroscopic line
parameters for CH
3
CN are not part of the HITRAN data-
base [
Rothman et al.
, 2005] and to the knowledge of the
authors no linelists exist that would be suitable for the
analysis of atmospheric observations with high spectral
resolution.
[
6
] The recent laboratory measurements of CH
3
CN at the
Pacific Northwest National Laboratory (PNNL) [
Rinsland et
al.
, 2005] provide absorption cross sections of much higher
quality (CH
3
CN absorption cross sections are available on
the HITRAN Web site, http://cfa-www.harvard.edu/
HITRAN/). These 29 spectra cover a region between 600
and 6500 cm
1
with a resolution of 0.1125 cm
1
, and were
measured at three different temperatures (276 K, 299 K, and
324 K). They were recorded with different CH
3
CN volume
mixing ratios (VMRs) at
1 atm pressure using N
2
as
pressure broadening gas.
[
7
] A pseudo-linelist with a pseudo-line spacing of
0.05 cm
1
was created by fitting the PNNL spectra simul-
taneously and iteratively adjusting the strengths and ground-
state energies of the pseudo-lines (see auxiliary material
1
).
1
Auxiliary material is available at ftp://ftp.agu.org/apend/gl/
2005GL024283.
GEOPHYSICAL RESEARCH LETTERS, VOL. 32, L23807, doi:10.1029/2005GL024283, 2005
C
o
p
y
r
i
g
h
t
2
0
0
5
b
y
t
h
e
A
m
e
r
i
c
a
n
G
e
o
p
h
y
s
i
c
a
l
U
n
i
o
n
.
0
0
9
4
-
8
2
7
6
/
0
5
/
2
0
0
5
G
L
0
2
4
2
8
3
L23807
1of5
The pseudo-linelist covers a spectral region between 870
and 1650 cm
1
, which includes the two bands with the
strongest absorption features at 1463.3 cm
1
and
1042.3 cm
1
, respectively (a copy of the pseudo-linelist is
available from the authors by request).
3. Analysis of Solar Occultation Spectra
3.1. Spectral Fitting
[
8
] In the following paragraphs we show analyses of
solar occultation measurements, taken with the JPL MkIV
Fourier transform interferometer. The MkIV covers a spec-
tral range between 650 and 5650 cm
1
with a spectral
resolution of
0.01 cm
1
. During balloon-borne operation,
the MkIV instrument views the sun through the atmospheric
limb at sunset or sunrise, hence providing a high sensitivity
to trace gases due to the long paths through the atmosphere.
[
9
] The present analysis comprises 12 balloon flights,
which were performed between 1993 and 2004. Five flights
were launched from Ft. Sumner, NM (34.5
°
N, 104.2
°
W),
one from Daggett, CA (34.9
°
N, 116.8
°
W), two from Fair-
banks, AK (64.8
°
N, 147.7
°
W), and four from Kiruna,
Sweden (67.9
°
N, 21.1
°
E). During a sunset or sunrise
measurement the duration of a single spectral scan leads
to a tangent altitude separation of typically
1kminthe
Arctic and 2–3 km at mid-latitudes. The measured sunset
and sunrise spectra ratios were obtained using an exo-
atmospheric spectrum derived from low-air mass measure-
ments from float altitude. The spectral fitting was performed
using a nonlinear least squares algorithm to determine the
slant column abundances of each target gas in each spec-
trum. For a more detailed description of the retrieval process
the reader is referred to
Sen et al.
[1996].
[
10
] Preliminary analyses showed that only the CH
3
CN
absorption feature at 1463.3 cm
1
is sufficiently strong to
warrant quantitative analysis at typical atmospheric CH
3
CN
concentrations. A frequency window between 1462.0 and
1464.4 cm
1
was chosen for analysis. This window
contains significant absorptions of CH
4
,H
2
O, HDO,
and HCN, so the amounts of these gases were adjusted
simultaneously with the CH
3
CN amount. Additionally, a
continuum level, a continuum tilt, a frequency shift, and a
zero level offset were adjusted during the fitting of the
atmospheric spectra.
[
11
] The H
2
O line parameters were taken from R. A.
Toth et al. (Air-broadening of H
2
O as a function of
temperature: 696 to 2163 cm
1
, submitted to
Journal of
Quantitative Spectroscopy and Radiative Transfer
, 2005).
The line parameters for the other gases were based on
HITRAN 2004 [
Rothman et al.
, 2005]. Initial spectral fits
revealed some systematic residuals inside the fitting
window. These were tracked down to errors in the CH
4
widths and positions. To remedy this deficiency, labora-
tory measurements of CH
4
from the Kitt Peak National
Solar Observatory were analyzed, and line positions and/
or broadening coefficients for some lines were adjusted
accordingly (see auxiliary material). Additionally a pseu-
do-linelist for the ethane band centered around 1500 cm
1
,
which is missing in HITRAN, was included to further
improve spectral fits.
[
12
] The diamond symbols in Figure 1d show the mea-
sured transmittance spectrum in the frequency window that
was analyzed. The major absorption features of CH
4
,H
2
O,
and HDO are identified. This particular spectrum was taken
on a balloon flight from Fairbanks, AK, on 8 May 1997 at a
tangent altitude of 11.96 km.
[
13
] Figure 1a shows the residual (measured spectrum -
calculated spectrum) of a fit to this measurement without
taking the CH
3
CN pseudo-linelist into account. The absorp-
tion feature of CH
3
CN around 1463.3 cm
1
can be clearly
identified. Other residuals present in Figure 1a correlate
with lines of CH
4
(1462.68 and 1463.03 cm
1
)orH
2
O
(1462.37 cm
1
).
[
14
] Figure 1b shows the residual when including the new
pseudo-linelist for CH
3
CN. The fit in the region around
1463.3 cm
1
improves considerably, the overall root-mean-
square error for the fit in the window decreases from 0.20%
to 0.13%. The solid line in Figure 1d shows the actual fit to
the measurement.
[
15
] Figure 1c shows the partial transmission attributed to
CH
3
CN. The absorption feature is about 2% deep at this
tangent altitude and its shape nicely matches the residual
around 1463.3 cm
1
in Figure 1a.
3.2. Profile Retrieval
[
16
] To retrieve a vertical profile of CH
3
CN we solve
the matrix equation that relates the measured slant col-
umns to the calculated geometrical slant paths on a
vertical grid of 2 km spacing. For this, a linear equation
solver is used together with a smoothing constraint.
Furthermore an a priori constraint is used for altitudes
above the balloon.
[
17
] Figure 2a shows the retrieved CH
3
CN profiles from
the 12 balloon flights. All profiles show VMRs around
100–150 ppt at low altitudes that decrease as altitude
increases. The highest altitude level given in Figure 2a is
the level where the error starts to exceed the retrieved value,
for mid-latitude profiles this is the case at 26–30 km, for
Figure 1.
Spectral fit to a MkIV limb transmittance
spectrum at a tangent altitude of 11.96 km during a solar
occultation measurement performed in May 1997.
a) Residual without CH
3
CN linelist. b) Residual including
CH
3
CN pseudo-linelist. c) Partial transmittance attributed to
CH
3
CN. d) Measured transmission spectrum (symbols) and
fit including CH
3
CN pseudo-linelist (solid line), and
identification of major absorption features.
L23807
KLEINBO
̈
HL ET AL.: INFRARED MEASUREMENTS OF CH
3
CN
L23807
2of5
Arctic profiles this altitude is typically lower (22–24 km).
The lowest usable altitude level is determined by the
amount of water vapor absorption in the spectrum. Below
a certain altitude some of the water vapor lines become very
strong and difficult to fit, which disturbs the retrieved
CH
3
CN. This altitude region starts typically below 16 km
at mid-latitudes and below 12 km in the Arctic.
[
18
] The two error bars given in Figure 2a show the
precisions derived from the spectral residuals that are
typical for retrievals in the Arctic and at mid-latitudes. In
the Arctic the precision is in the order of 15–25 ppt, mainly
due to longer occultation durations (1–2 hours). At mid-
latitudes the shorter occultation duration (
35 minutes)
leads to precisions around 25–35 ppt.
[
19
] Regarding the absolute accuracy of the retrievals, a
fit to the 29 PNNL laboratory spectra shows that the
pseudolines correctly represent the spectra to within 0.7%
of the given CH
3
CN amount in this frequency region (see
auxiliary material). We note that an additional uncertainty
may arise from the extrapolation of the temperature
dependence of the pseudolines from laboratory temper-
atures to atmospheric temperatures (
220 K). Cross
comparisons between different laboratory measurements
for several species suggest that the accuracy of the
infrared cross-sections used to derive the pseudo-linelist
should be in the order of 1.7% [
Sharpe et al.
, 2004].
Other contributions to the uncertainty are interferences
with other gases. In the case of the CH
3
CN retrieval these
are mainly CH
4
and H
2
O. Assuming that the improve-
ments of the line parameters for the CH
4
are erroneous
by 20% leads to a change in CH
3
CN VMR of
2.5%.
For H
2
O the strongest influence is expected to be due to
the air broadening and its temperature dependence of the
strong H
2
O line at 1464.905 cm
1
. The uncertainty of
these parameters leads to an additional uncertainty in the
CH
3
CN VMR of
1%.
4. Discussion
[
20
] In the lower stratosphere the profiles retrieved from
the MkIV spectra show VMRs around 100–150 ppt
(Figure 2a). This compares well to the range given by
airborne in-situ measurements in the lowermost stratosphere
[
Schneider et al.
, 1997] and the upper troposphere [
Singh et
al.
, 2003]. It has to be noted that these values are signifi-
cantly higher than earlier in-situ measurements [e.g.,
Knop
and Arnold
, 1987] and the upper limit obtained from
ground-based infrared measurements [
Muller
, 1985]. They
are also higher than the MLS measurements from the 1990s
[
Livesey et al.
, 2001] which did not exceed
50 ppt in the
extratropical lower stratosphere.
[
21
] In the middle stratosphere the mid-latitude MkIV
profiles tend to exceed in-situ balloon measurements
summarized by
Brasseur et al.
[1983] while the error
bars of the Arctic MkIV profiles overlap with the range
given by these measurements. All profiles show a de-
creasing CH
3
CN VMR with increasing altitude. Due to
the limited precision of the measurements no trend is
derived from this data set.
[
22
] The mid-latitude VMRs generally exceed the Arc-
tic VMRs at the same altitude, reflecting the large scale
circulation of air in the stratosphere (i.e. ascending air
motion in the tropics and descending air motion in the
polar regions). The lower values are particularly visible in
the measurements of Dec. 1999, Mar. 2000, and Dec.
2002, which took place inside the Arctic polar vortex
Figure 2.
Retrieved vertical profiles of CH
3
CN from
12 balloon flights between 1993 and 2004 vs. a) altitude,
b) CH
3
Cl, and c) CH
4
, measured simultaneously in the same
air mass by the MkIV instrument. The error bars give
typical precisions for measurements at mid-latitudes (red)
and in the Arctic (green). Black solid lines indicate
measurements from literature sources (Sin03: mean and
std. dev. of airborne gas chromatographic measurements in
the upper troposphere [
Singh et al.
, 2003], Sch97: range of
airborne mass spectrometric measurements in the lowermost
stratosphere assuming a tropopause altitude of 10 km
[
Schneider et al.
, 1997], Bra83: range of balloon-borne
mass spectrometric measurements summarized by
Brasseur
et al.
[1983]). Black dashed and dotted lines show profiles
calculated with a 2D model.
L23807
KLEINBO
̈
HL ET AL.: INFRARED MEASUREMENTS OF CH
3
CN
L23807
3of5
where significant diabatic descent of the air masses had
occurred.
[
23
] We compare the measured CH
3
CN profiles with
output of a 2D-model [
Rinsland et al.
, 2003] that uses
gas-phase, non-ion CH
3
CN chemistry (see auxiliary mate-
rial). Figure 2a shows modeled CH
3
CN profiles for 15 Sep.
at 35
°
N and 15 Mar. at 70
°
N. The modeled profiles agree
very well with the measurements in both mid-latitude and
Arctic regions.
[
24
] Figures 2b and 2c show the MkIV CH
3
CN profiles
vs. the tracers CH
3
Cl and CH
4
retrieved from the same
MkIV balloon measurements. The sources of both tracers
are in the troposphere, and the destruction in the strato-
sphere occurs mainly by the reaction with OH. Considering
CH
3
CN VMRs on isopleths of CH
3
Cl or CH
4
should
remove the variability induced by the large scale atmo-
spheric circulation [
Plumb and Ko
, 1992]. The correlations
of CH
3
CN with CH
3
Cl and CH
4
are more compact than the
correlation with altitude, confirming the tracer character-
istics of CH
3
CN in the stratosphere. We note that the
CH
3
CN VMRs on isopleths >500 ppt CH
3
Cl compare well
to the correlation derived from in-situ data in the upper
troposphere [
Singh et al.
, 2003].
[
25
] Also included in Figures 2b and 2c are the modeled
correlations of CH
3
CN with CH
3
Cl and CH
4
. The agree-
ment with the observed CH
3
CN-tracer correlations is ex-
cellent. This shows that the model correctly calculates the
loss of CH
3
CN in the stratosphere by using the established
gas-phase reactions.
[
26
]
Schneider et al.
[1997] concluded from an ob-
served decrease of CH
3
CN in the lowest 4 km above the
tropopause that the lifetime of CH
3
CN should not be
much longer than the timescale for vertical mixing (<
1
yr). The compact correlation between CH
3
CN and the
tracers derived in this work indicates that CH
3
CN is
rather long-lived, with a modeled lifetime of about 10–
20 years in the lower stratosphere. This suggests that the
ion-molecule reactions proposed by
Schneider et al.
[1997] do not play a major role as loss processes of
CH
3
CN.
5. Summary and Outlook
[
27
] For the first time CH
3
CN has been measured in the
Earth’s atmosphere by means of infrared remote sensing.
Vertical profiles were derived in an altitude range of about
12–30 km with a precision of
20 ppt in the Arctic and
30 ppt at mid-latitudes. The retrieved CH
3
CN profiles
show VMRs of 100–150 ppt a few kilometers above the
tropopause that decrease with altitude, reaching values
below 40 ppt at altitudes between 22 and 30 km. The
CH
3
CN VMRs reveal a reasonably compact correlation
with the tracers CH
3
Cl and CH
4
in the considered altitude
range, and are in excellent agreement with the 2D-model,
which suggests that the known, gas-phase loss mechanisms
are fully adequate to explain the abundance of CH
3
CN in
the stratosphere.
[
28
] The demonstration of the retrieval of CH
3
CN
vertical profiles in the infrared gives rise to several
applications. We expect a retrieval of the kind presented
here to be feasible for satellite remote measurements by
the Atmospheric Chemistry Experiment (ACE) [
Bernath
et al.
, 2005], with the potential to give a global view on
the distribution of CH
3
CN and to investigate the strato-
spheric source in the tropics suggested by
Livesey et al.
[2001]. The data presented in this paper will be a useful
source for validation information for the satellite experi-
ments ACE and the EOS MLS, which are currently in
orbit. It is expected that detection of CH
3
CN in the
infrared will be feasible also on spaceborne missions to
other objects in the solar system, in particular Saturn’s
moon Titan, where CH
3
CN has already been detected by
microwave techniques [
Bezard et al.
, 1993;
Marten et al.
,
2002].
[
29
]
Acknowledgments.
We would like to thank the various launch
crews for conducting the balloon flights, and to D. Petterson and J. Landeros
of JPL for their excellent support prior and during the measurement
campaigns. We also wish to thank S. Sharpe and C. Rinsland for providing
their CH
3
CN absorption cross sections prior to publication, and
A. Goldman and I. Kleiner for valuable discussions about the CH
3
CN
partition function. Thanks also to J. Margolis, L. Brown, and again
C. Rinsland for laboratory spectra from Kitt Peak. Work at AER was
supported by the NASA Atmospheric Chemistry Modeling and Analysis
Program. Work at the Jet Propulsion Laboratory, California Institute of
Technology, was performed under a contract with the National Aeronautics
and Space Administration.
References
Arjis, E., and G. Brasseur (1986), Acetonitrile in the stratosphere and impli-
cations for positive ion composition,
J. Geophys. Res.
,
91
, 4003–4016.
Arnold, F., H. Bo
̈hringer, and G. Henschen (1978), Composition measure-
ments of stratospheric positive ions,
Geophys. Res. Lett.
,
5
, 642–644.
Bernath, P. F., et al. (2005), Atmospheric Chemistry Experiment (ACE):
Mission overview,
Geophys. Res. Lett.
,
32
, L15S01, doi:10.1029/
2005GL022386.
Bezard, B., A. Marten, and G. Paubert (1993), Detection of acetonitrile on
Titan,
Bull. Am. Astron. Soc.
,
25
, 1100.
Brasseur, G., E. Arjis, A. De Rudder, D. Nevejans, and J. Ingels (1983),
Acetonitrile in the atmosphere,
Geophys. Res. Lett.
,
10
, 725–728.
Hamm, S., and P. Warneck (1990), The interhemispheric distribution and
the budget of acetonitrile in the troposphere,
J. Geophys. Res.
,
95
,
20,593–20,606.
Hamm, S., J. Hahn, G. Helas, and P. Warneck (1984), Acetonitrile in the
troposphere,
Geophys. Res. Lett.
,
11
, 1207–1210.
Knop, G., and F. Arnold (1987), Stratospheric trace gas detection using a
new balloon-borne ACIMS method: Acetonitrile, acetone, and nitric acid,
Geophys. Res. Lett.
,
14
, 1262–1265.
Livesey, N. J., J. W. Waters, R. Khosravi, G. P. Brasseur, G. S. Tyndall, and
W. G. Read (2001), Stratospheric CH
3
CN from UARS MLS,
Geophys.
Res. Lett.
,
28
, 779–782.
Livesey, N. J., M. D. Fromm, J. W. Waters, G. L. Manney, M. L. Santee,
and W. G. Read (2004), Enhancements in lower stratospheric CH3CN
observed by the UARS MLS following boreal forest fires,
J. Geophys.
Res.
,
109
, D06308, doi:10.1029/2003JD004055.
Marten, A., T. Hidayat, Y. Biraud, and R. Morenco (2002), New millimeter
heterodyne observations of Titan: Vertical distributions of nitriles HCN,
HC
3
N, CH
3
CN, and the isotopic ratio
15
N/
14
N in its atmosphere,
Icarus
,
158
, 532–544.
Muller, C. (1985), Acetonitrile in the Earth’s atmosphere: An upper limit
deduced from infrared solar spectra,
Bull. Cl. Sci. Acad. R. Belg.
,
71
,
225–229.
Plumb, R. A., and M. K. W. Ko (1992), Interrelationships of mixing ratios
between long-lived stratospheric constituents,
J. Geophys. Res.
,
97
,
10,145–10,156.
Rinsland, C. P., D. K. Weisenstein, M. K. W. Ko, C. J. Scott, L. S.
Chiou, E. Mahieu, R. Zander, and P. Demoulin (2003), Post-Mount
Pinatubo eruption ground-based infrared stratospheric column measure-
ments of HNO
3
,NO,andNO
2
and their comparison with model
calculations,
J. Geophys. Res.
,
108
(D15), 4437, doi:10.1029/
2002JD002965.
Rinsland, C. P., S. W. Sharpe, and R. L. Sams (2005), Temperature-
dependent infrared absorption cross-sections of methyl cyanide,
J. Quant.
Spectrosc. Radiat. Transfer
,
96
, 271–280.
Rothman, L. S., et al. (2005), The HITRAN 2004 molecular spectroscopic
data base,
J. Quant. Spectrosc. Radiat. Transfer
,
96
, 139–204.
L23807
KLEINBO
̈
HL ET AL.: INFRARED MEASUREMENTS OF CH
3
CN
L23807
4of5
Schneider, J., V. Bu
̈rger, and F. Arnold (1997), Methyl cyanide and hydro-
gen cyanide measurements in the lower stratosphere,
J. Geophys. Res.
,
102
, 25,501–25,506.
Sen, B., G. C. Toon, J.-F. Blavier, E. L. Fleming, and C. H. Jackman
(1996), Balloon-borne observations of midlatitude flourine abundances,
J. Geophys. Res.
,
101
, 9045–9054.
Sharpe, S. W., T. Johnson, R. Sams, P. Chu, G. Rhoderick, and P. Johnson
(2004), Gas-phase databases for quantitative infrared spectroscopy,
Appl.
Spectrosc.
,
58
, 1452–1461.
Singh, H. B., et al. (2003), In situ measurements of HCN and CH
3
CN over
the Pacific Ocean: Sources, sinks, and budgets,
J. Geophys. Res.
,
108
(D20), 8795, doi:10.1029/2002JD003006.
Toon, G. C. (1991), The JPL Mk IV interferometer,
Opt. Photonics News
,
2
,
19–21.
Tyndall, G. S., J. J. Orlando, T. J. Wallington, and M. D. Hurley (2001),
Products of the chlorine-atom- and hydroxyl-radical-initiated oxidation of
CH
3
CN,
J. Phys. Chem. A
,
105
, 5380–5384.
J.-F. L. Blavier, A. Kleinbo
̈hl, B. Sen, and G. C. Toon, Jet Propulsion
Laboratory, MS 183-501, 4800 Oak Grove Drive, Pasadena, CA 91109,
USA. (armin.kleinboehl@jpl.nasa.gov)
D. K. Weisenstein, Atmospheric and Environmental Research, Inc., 131
Hartwell Avenue, Lexington, MA 02421, USA.
P. O. Wennberg, Division of Engineering and Applied Sciences,
California Institute of Technology, 1200 East California Boulevard,
Pasadena, CA 91125, USA.
L23807
KLEINBO
̈
HL ET AL.: INFRARED MEASUREMENTS OF CH
3
CN
L23807
5of5