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Recent knowledge of spectroscopic parameters for
Acetylene in the IR D. Jacquemart,a N. Lacome, a
V. Dana,b J.-Y. Mandin b, O.M. Lyulin c, V.I.
Perevalov c, L. Régalia-Jarlot d, X. Thomas d, P.
Von Der Heyden d a Laboratoire de Dynamique,
Interactions et Réactivité, Université
Pierre-et-Marie Curie, CNRS, UMR 7075, Case
courrier 49, 4, place Jussieu, 75252 Paris Cedex
05, France b Laboratoire de Physique Moléculaire
pour lAtmosphère et lAstrophysique, Université
Pierre-et-Marie-Curie, CNRS, UMR 7092, Case
courrier 76,4, place Jussieu,75252 Paris Cedex
05, France c Institute of Atmospheric Optics,
Siberian Branch, Russian Academy of Sciences, 1,
Akademicheskii av.,634055 Tomsk, Russia d Groupe
de Spectrométrie Moléculaire et Atmosphérique,
Université de Reims-Champagne-Ardenne, CNRS, BP
1039, 51687 Reims Cedex, France.
PRESENTATION The acetylene molecule is
important for atmospheric, planetary, and
astrophysics applications. In order to improve
the knowledge of C2H2 spectroscopic parameters,
systematic measurements of line parameters have
been performed. Three recent works in three
different spectral regions are presented in the
3.8-µm region, where 2 cold and 3 hot bands have
been studied 1 in the 2.5-µm region, where 4
cold and 5 hot bands have been studied 2 in
the 2.2-µm region, where 4 cold and 4 hot bands
have been studied 3. Line positions and
intensities have been analysed. In these three
spectral regions, transition dipole moments
squared values have been derived from the line
intensity measurements, and have been modelled
using Herman-Wallis factors. No analysis of
absolute individual line intensities in these
three regions has been done before these present
works. Line lists have been generated and will
be proposed to atmospheric and planetary
spectroscopic databases. The analysis of these
spectral region has also allowed to improve the
global theoretical treatment 4-5 of Perevalov
et al. adapted to the Hamiltonian and transition
dipole moment of acetylene 12C2H2 (interacting
vibrational states belonging to different polyads
are taken into account through cold and hot
bands). According to Perevalovs notation, the
studied spectral region concerns the series of
vibrational transitions ?P  4, 6 and 7 with P
the pseudo-quantum number P  5v1  3v2  5v3  
v4  v5 .
MEASUREMENT PROCEDURE To retrieve absolute line
positions and intensities from the spectra, a
multispectrum fitting procedure 6 has been
used. Because of the wide variety of the line
strength values, the best experimental conditions
for an accurate analysis are obtained only for
two or three spectra. Due to the flexibility of
the multispectrum procedure, we were able to
adjust simultaneously all experimental spectra.
Let us recall that the position, intensity, and
broadening coefficient of a same line in the five
spectra keep the same values during the fit. In
a first step, a wavenumber calibration has been
done separately for the three spectral regions.
Transitions of the ?3 band of 12C16O2 has been
used for the 3.8-µm spectral region H2O
transitions and C2H2 transitions respectively for
the 2.5- and 2.2-µm spectral regions. e
(sHITRAN2004 - sthis work )/ sHITRAN2004 has been
calculated for isolated transitions in each
spectrum. Combining the absolute accuracy from
HITRAN2004 and the statistic deviation of our
wavenumber calibration, we estimated that the
absolute accuracy of the measured positions is
around 0.0005 cm-1. As an example of the
capability of our multispectrum fitting
procedure, this figure shows a simultaneous fit
of the Q-branch of the ?2 ?51 of 12C2H2 in 4
spectra recorded at different pressures. The
calculated spectra reproduce very well each
experimental spectrum. For each of them, the
residuals (obs-calc) of the fit are quite good
despite the two channels (due to windows) present
in the experimental spectra. The residuals of
the fit do not exceed 2.
v1  3373 cm-1 v2  1974 cm-1 v3  3294 cm-1
v4  613 cm-1 v5 730 cm-1
CONCLUSION Several collaborations between LADIR,
LPMAA, GSMA, and LTS has led to the better
knowledge of the acetylene IR spectroscopic
parameters in the 2.2, 2.5, and 3.8-µm spectral
regions. The experimental results in the 2.5 and
3.8-µm regions have allowed the generation of
line lists with calculated positions (obtained
from polynomial fits of measurements), and
calculated intensities (using the transition
dipole moment and the Herman-Wallis coefficients
of each band). This has not been done for the
2.2-µm region where strong interactions between
levels do not allow accurate fit using
Herman-Wallis coefficients. All the measurements
have then been used to treat the ?P 4, 6 and 7
series. The first results are encouraging, but
at that time the precision of the line positions
and intensities obtained using treatment of the
Hamiltonian and the transition dipole moment, is
not enough accurate compared to the one from
experimental measurements. The global model of
acetylene done by LTS (Perevalov et al.) still
need some improvement, and measurements to
achieve the experimental accuracy that is better
than 10-3 cm-1 for positions, and 5 for line
intensities. Note that, the predictability of
this model was successfully tested on two hot
bands of the 2.5-µm region 2.
References 1 D. Jacquemart, N. Lacome, J.-Y.
Mandin, V. Dana, O.M. Lyulin, V.I. Perevalov.
Multispectrum fitting of line parameters for
12C2H2 in the 3.8-µm spectral region. (submitted
to JQSRT) 2 O.M. Lyulin, V.I. Perevalov, J.-Y.
Mandin, V. Dana, F. Gueye, X. Thomas, P. Von Der
Heyden, D. Décatoire, L. Régalia-Jarlot, D.
Jacquemart, N. Lacome. Line intensities of
acetylene Measurements in the 2.5-µm spectral
region and global modeling in the ?P  4 and 6
series. (submitted to JQSRT) 3 O.M. Lyulin A,
V.I. Perevalov, F. Gueye, J.-Y. Mandin, V. Dana,
X. Thomas, P. Von Der Heyden, L. Régalia-Jarlot,
A. Barbe. Line intensities of acetylene.
Measurements in the 2.2-µm spectral region and
global modeling in the ?P 7 series (under
editing)4 O.M. Lyulin, V.I. Perevalov, S.A.
Tashkun, and J.-L. Teffo. Global fitting of the
vibrational-rotational line positions of
acetylene molecule in the far and middle infrared
regions. In Proceedings of the XIVth Symposium
on High-Resolution Molecular Spectroscopy,
Krosnoyarsk, Russia. SPIE 5311, 134-143
(2004). 5 V.I. Perevalov, O.M. Lyulin, D.
Jacquemart, C. Claveau, J.-L. Teffo, V. Dana,
J.-Y. Mandin, and A. Valentin. Global fitting of
line intensities of acetylene molecule in the
infrared using the effective operator approach.
J Mol Spectrosc 218, 180-189 (2003). 6  D.
Jacquemart, J.-Y. Mandin, V. Dana, N. Picqué, and
G. Guelachvili. A multispectrum fitting
procedure to deduce molecular line parameters.
Application to the 3?0 band of 12C16O. Eur Phys
J D 14, 55-69 (2001).