J/MNRAS/399/425 (De)excitation rates of ortho-NH3 and para-NH3 (Faure+, 2009)
On the robustness of the ammonia thermometer.
Maret S., Faure A., Scifoni E., Wiesenfeld L.
<Mon. Not. R. Astron. Soc. 399, 425 (2009)>
=2009MNRAS.399..425M 2009MNRAS.399..425M
ADC_Keywords: Atomic physics
Keywords: molecular data - molecular processes - ISM: molecules
Abstract:
Ammonia inversion lines are often used as probes of the physical
conditions in the dense ISM. The excitation temperature between the
first two para metastable (rotational) levels is an excellent probe of
the gas kinetic temperature. However, the calibration of this ammonia
thermometer depends on the accuracy of the collisional rates with H2.
Here we present new collisional rates for ortho-NH3 and para-NH3
colliding with para-H2 (J=0) and we investigate the effects of these
new rates on the excitation of ammonia. Scattering calculations employ
a new, high accuracy, potential energy surface computed at the
coupled-cluster CCSD(T) level with a basis set extrapolation
procedure. Rates are obtained for all transitions involving ammonia
levels with J≤3 and for kinetic temperatures in the range 5-100K.
We find that the calibration curve of the ammonia thermometer -- which
relates the observed excitation temperature between the first two para
metastable levels to the gas kinetic temperature -- does not change
significantly when these new rates are used. Thus, the calibration of
ammonia thermometer appears to be robust. Effects of the new rates on
the excitation temperature of inversion and rotation-inversion
transitions are also found to be small.
Description:
For ortho- and para-NH3, 15 and 45 *downward* rotational rates are
provided, corresponding to all possible transitions among their 6 and
10 lowest levels, respectively. 20 temperatures in the range 5-100K
are considered. Upward rates can be computed using the detailed
balance relation (see paper). Level energies are from the JPL
catalog.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
onh3lev.dat 37 6 Energy levels of ortho-NH3, in cm-1
pnh3lev.dat 37 10 Energy levels of para-NH3, in cm-1
onh3ph2.dat 208 15 De-excitation rates (in cm3/s) of ortho-NH3
in collision with para-H2
pnh3ph2.dat 208 45 De-excitation rates (in cm3/s) of para-NH3 in
collision with para-H2
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See also:
J/A+A/472/1029 : (De)excitation rates of H2O by H2 (Faure+, 2007)
J/A+A/492/257 : Collisional excitation of water in warm media (Faure+, 2008)
J/A+A/493/687 : Rotational excitation of formaldehyde by H2 (Faure+, 2009)
Byte-by-byte Description of file(#): onh3lev.dat pnh3lev.dat
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Bytes Format Units Label Explanations
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1- 5 I5 --- Level [1,10] level number
6- 21 F16.9 cm-1 E level energy
22- 28 F7.1 --- F statistical weight
29- 37 A9 --- N quantum numbers
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Byte-by-byte Description of file(#): onh3ph2.dat pnh3ph2.dat
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Bytes Format Units Label Explanations
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1- 2 I2 --- Trans [1,45] Transition number
4- 5 I2 --- i [2,10] Initial level
7- 8 I2 --- f [1,10] Final level
10- 18 E9.3 cm3/s k5 Rate coefficient at 5K
20- 28 E9.3 cm3/s k10 Rate coefficient at 10K
30- 38 E9.3 cm3/s k15 Rate coefficient at 15K
40- 48 E9.3 cm3/s k20 Rate coefficient at 20K
50- 58 E9.3 cm3/s k25 Rate coefficient at 25K
60- 68 E9.3 cm3/s k30 Rate coefficient at 30K
70- 78 E9.3 cm3/s k35 Rate coefficient at 35K
80- 88 E9.3 cm3/s k40 Rate coefficient at 40K
90- 98 E9.3 cm3/s k45 Rate coefficient at 45K
100-108 E9.3 cm3/s k50 Rate coefficient at 50K
110-118 E9.3 cm3/s k55 Rate coefficient at 55K
120-128 E9.3 cm3/s k60 Rate coefficient at 60K
130-138 E9.3 cm3/s k65 Rate coefficient at 65K
140-148 E9.3 cm3/s k70 Rate coefficient at 70K
150-158 E9.3 cm3/s k75 Rate coefficient at 75K
160-168 E9.3 cm3/s k80 Rate coefficient at 80K
170-178 E9.3 cm3/s k85 Rate coefficient at 85K
180-188 E9.3 cm3/s k90 Rate coefficient at 90K
190-198 E9.3 cm3/s k95 Rate coefficient at 95K
200-208 E9.3 cm3/s k100 Rate coefficient at 100K
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Acknowledgements:
Alexandre Faure, afaure(at)obs.ujf-grenoble.fr
(End) Alexandre Faure [LAOG, France], Patricia Vannier [CDS] 24-Sep-2009