J/A+A/376/356 Diatomic molecules collisional rates (Chandra+, 2001)
Collisional rates for vib-rotational transitions in diatomic molecules.
Chandra S., Sharma A.K.
<Astron. Astrophys. 376, 356 (2001)>
=2001A&A...376..356C 2001A&A...376..356C
ADC_Keywords: Atomic physics
Keywords: molecular data - stars: circumstellar matter
Abstract:
A number of diatomic molecules have been found in vibrationally
excited states in several cosmic objects. The molecules in
vibrationally excited states provide valuable information about the
physical conditions prevailing near star forming regions and in
circumstellar envelopes of late-type stars. To analyze the spectrum of
such molecules, some of the important parameters required are the
collisional rate coefficients for vib-rotational transitions in the
molecule. Currently, knowledge of collisional rate coefficients is
very poor. Here, we discuss a method for calculating the collisional
rate coefficients for vib-rotational transitions in a diatomic
molecule, where the colliding partner H2 is considered as a
structureless particle. This method is quite good for high
temperatures (usually found in star-forming regions and in
circumstellar envelopes of late-type stars), but may be questioned for
low temperatures. As an example, calculations for the CS molecule at
500K for three vibrational states are presented.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 21 118 Energy, statistical weight, vibrational quantum
number, and rotational quantum number of energy
levels
table3.dat 39 6786 Collisional rate coefficients for the transition
from the upper to the lower level
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See also:
J/A+AS/114/175 : Einstein A-coefficients in CS transitions (Chandra+ 1995)
J/A+AS/117/557 : Einstein coefficients for CO transitions (Chandra+ 1996)
J/A+AS/131/137 : Einstein A-Coefficients in SiC2 transitions (Chandra+ 1998)
J/A+AS/142/113 : C3H2 and SiC2 collisional rates (Chandra+, 2000)
J/A+A/376/333 : Einstein A-coefficients for C3H4 (Sharma+, 2001)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 3 I3 --- No Serial number
5- 13 F9.4 cm-1 E Energy
15- 16 I2 --- SWeigth Statistical weight
18 I1 --- v Vibrational quantum number of energy level
20- 21 I2 --- J Rotational quantum number of energy level
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [(] (1)
2 I1 --- vu Vibrational quantum number of upper level (1)
3 A1 --- --- [,] (1)
5- 6 I2 --- ju Rotational quantum number of upper level (1)
7 A1 --- --- [)] (1)
9- 11 A3 --- --- [⟹] (1)
13 A1 --- --- [(] (1)
14 I1 --- vl Vibrational quantum number of lower level (1)
15 A1 --- --- [,] (1)
17- 18 I2 --- jl Rotational quantum number of lower level (1)
19 A1 --- --- [)] (1)
22- 29 E8.4 cm3/s Rate Collisional rate coefficient from u to l
32- 34 I3 --- u Upper level
37- 39 I3 --- l Lower level
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Note (1): Name of the transition between the upper level with vibrational
quantum number vu and rotational quantum number ju and the lower level
with vibrational quantum number vl and rotational quantum number jl,
(vu, ju) ⟹ (vl, jl)
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Acknowledgements: S. Chandra <chandrasuresh@123india.com>
(End) Patricia Bauer [CDS] 27-Aug-2001