J/A+A/531/A103 Collisional excitation of sulfur dioxide (Cernicharo+, 2011)
Collisional excitation of sulfur dioxide, SO2, in cold molecular clouds.
Cernicharo J., Spielfiedel A., Balanca C., Dayou F., Senent M.-L.,
Feautrier N., Faure A., Cressiot-Vincent L., Wiesenfeld L., Pardo J.R.
<Astron. Astrophys. 531, A103 (2011)>
=2011A&A...531A.103C 2011A&A...531A.103C
ADC_Keywords: Atomic physics ; Molecular clouds
Keywords: molecular processes - ISM : molecules - ISM : abundances
Abstract:
We present collisional rate coefficients for SO2 with ortho and para
molecular hydrogen for the physical conditions prevailing in dark
molecular clouds. Rate coefficients for the first 31 rotational levels
of this species (energies up to 55K) and for temperatures between 5
and 30K are provided. We have found that these rate coefficients are
about ten times more than those previously computed for SO2 with
helium. We calculated the expected emission of the centimeter
wavelength lines of SO2. We find that the transition connecting the
metastable 202 level with the 111 one is in absorption against the
cosmic background for a wide range of densities. The 404-313
line is found to be inverted for densities below a few 104cm-3. We
observed the 111-202 transition with the 100m Green Bank
Telescope towards some dark clouds. The line is observed, as expected,
in absorption and provides an abundance of SO2 in these objects of a
few 10-10. The potential use of millimeter lines of SO2 as tracers
of the physical conditions of dark clouds is discussed.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 27 31 SO2 calculated energy levels
table5.dat 71 961 Rate coefficients of SO2 in collision with
para-H2(j2=0,2) as function of kinetic temperature
table6.dat 71 961 Rate coefficients of SO2 in collision with
ortho-H2(j2=1) as function of kinetic temperature
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Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Level Level number
4- 11 A8 --- Trans j(Ka,Kc) value
13- 19 F7.4 cm-1 E This work energy level
21- 27 F7.4 cm-1 EJPL JPL energy level (1)
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Note (1): Pickett et al., 1998,J. Quant. Spectrosc. Rad. Transfer 60, 883
see also JPL Molecular Spectroscopy Catalog: http://spec.jpl.nasa.gov
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Byte-by-byte Description of file: table5.dat table6.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- I Initial level
4- 5 I2 --- F Final level
7- 16 E10.5 cm3/s Rate(5) Rate coefficient at temperature Tkin=5K
18- 27 E10.5 cm3/s Rate(10) Rate coefficient at temperature Tkin=10K
29- 38 E10.5 cm3/s Rate(15) Rate coefficient at temperature Tkin=15K
40- 49 E10.5 cm3/s Rate(20) Rate coefficient at temperature Tkin=20K
51- 60 E10.5 cm3/s Rate(25) Rate coefficient at temperature Tkin=25K
62- 71 E10.5 cm3/s Rate(30) Rate coefficient at temperature Tkin=30K
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Acknowledgements:
Nicole Feautrier, Nicole.Feautrier(at)obspm.fr
(End) Patricia Vannier [CDS] 04-May-2011