J/ApJS/216/3 H2O:He collisions between 20-120K (Tejeda+, 2015)
Laboratory study of rate coefficients for H2O:He inelastic collisions
between 20 and 120 K.
Tejeda G., Carmona-Novillo E., Moreno E., Fernandez J.M., Hernandez M.I.,
Montero S.
<Astrophys. J. Suppl. Ser., 216, 3 (2015)>
=2015ApJS..216....3T 2015ApJS..216....3T
ADC_Keywords: Atomic physics
Keywords: astronomical databases: miscellaneous; ISM: molecules;
methods: laboratory: molecular; molecular processes;
techniques: spectroscopic
Abstract:
State-to-state rate coefficients for ortho-H2O:He and para-H2O:He
inelastic collisions in the 20-120K thermal range are investigated by
means of an improved experimental procedure. This procedure is based
on the use of a kinetic master equation (MEQ) which describes the
evolution of populations of H2O rotational levels along a supersonic
jet of H2O highly diluted in helium. The MEQ is expressed in terms
of experimental observables and rate coefficients for H2O:He
inelastic collisions. The primary experimental observables are the
local number density and the populations of the rotational energy
levels of H2O, quantities which are determined along the jet with
unprecedented accuracy by means of Raman spectroscopy with high space
resolution. Sets of rate coefficients from the literature and from
present close-coupling calculations using two different potential
energy surfaces (PESs) have been tested against the experiment. The
Green et al. (VI/59) rate coefficients are up to 50% too low compared
to the experiment, while most rates calculated here from the Hodges et
al. (2002JChPh.116.1397H 2002JChPh.116.1397H) PES and the Patkowski et al. (2002, JMoSt
TEOCHEM, 591, 231) PES are much closer to the experimental values.
Experimental rates with an estimated accuracy on the order of 10% have
been obtained for ortho-H2O:He and para-H2O:He inelastic
collisions between 20 and 120K by scaling and averaging the
theoretical rates to the experiment.
Description:
Experimental work has been conducted in one of the two dedicated
facilities for quantitative gas diagnostics which are operative at the
Laboratory of Molecular Fluid Dynamics (IEM-CSIC, Madrid).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 63 816 Calculated and experiment-scaled k_l->i rates for
ortho and para-H2O:He collisions
table4.dat 74 136 Experimental kSEl->i deexcitation rates for
ortho and para-H2O:He collision
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See also:
VI/59 : COLLISIONAL EXCITATION RATES FOR INTERSTELLAR WATER (Green+, 1993)
J/A+A/492/257 : Collisional excitation of water in warm media (Faure+, 2008)
Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Type H2O molecule type ("ortho" or "para")
7- 8 I2 --- l [2/13] Initial rotational state (G1)
10 I1 --- i [1/8] Final rotational state (G1)
12 I1 --- Jl [1/5] Rotational quantum number of initial state
14 I1 --- Ji [0/4] Rotational quantum number of final state
16- 20 F5.1 cm-1 El-Ei [1.9/384] Approximate collision energy gap
22- 24 I3 K Tt [20/120] Translational temperature
26- 29 I4 10-14cm3/s GratC Calculated G-rate from G-PES (1)
31- 34 I4 10-14cm3/s HratC Calculated H-rate from H-PES (1)
36- 39 I4 10-14cm3/s PratC Calculated P-rate from P-PES (1)
41- 44 I4 10-14cm3/s GratE Experiment-scaled G-rate from G-PES (2)
46- 49 I4 10-14cm3/s HratE Experiment-scaled H-rate from H-PES (2)
51- 54 I4 10-14cm3/s PratE Experiment-scaled P-rate from P-PES (2)
56- 59 I4 10-14cm3/s kSE [0/3512] Averaged experimental rate (2)
61- 63 I3 10-14cm3/s e_kSE [1/265] Estimated 1σ uncertainty in kSE (3)
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Note (1): Three sets of state-to-state (STS) rates are tested in the present
work, namely, that by Green et al. (1993, Cat. VI/59) and those
calculated in the present work within the close-coupling approach by
employing the MOLSCAT code (Hutson & Green, 1994, version 14,
Distributed by Collaborative Computational Project No. 6 of the UK
Science and Engineering Research Council (UK)), with the H-PES
(potential energy surface (PES); SIII surface) of Hodges et al.
(2002JChPh.116.1397H 2002JChPh.116.1397H) and the P-PES of Patkowski et al. (2002,
JMoSt TEOCHEM, 591, 231). These three sets of theoretical STS rates
are referred to as G-rates, H-rates, and P-rates.
Note (2): Corrected by H2O:H2O selfcollisions.
Note (3): Defined according to Eq. (6) incremented by 3% due to the error
from H2O:H2O selfcollisions.
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 5 A5 --- Type Molecule type (ortho or para)
7- 8 I2 --- l [2/13] Initial rotational state (G1)
10 I1 --- i [1/8] Final rotational state (G1)
12 I1 --- Jl [1/5] Rotational quantum number of initial state
14 I1 --- Ji [0/4] Rotational quantum number of final state
16- 20 F5.1 cm-1 El-Ei [1.9/384] Approximate collision energy gap
22- 25 I4 10-14cm3/s E20 Experimental kSEl->i rate at 20K (1)
27- 29 I3 10-14cm3/s e_E20 The 1σ uncertainty in E20 (2)
31- 34 I4 10-14cm3/s E40 Experimental kSEl->i rate at 40K (1)
36- 38 I3 10-14cm3/s e_E40 The 1σ uncertainty in E40 (2)
40- 43 I4 10-14cm3/s E60 Experimental kSEl->i rate at 60K (1)
45- 47 I3 10-14cm3/s e_E60 The 1σ uncertainty in E60 (2)
49- 52 I4 10-14cm3/s E80 Experimental kSEl->i rate at 80K (1)
54- 56 I3 10-14cm3/s e_E80 The 1σ uncertainty in E80 (2)
58- 61 I4 10-14cm3/s E100 Experimental kSEl->i rate at 100K (1)
63- 65 I3 10-14cm3/s e_E100 The 1σ uncertainty in E100 (2)
67- 70 I4 10-14cm3/s E120 Experimental kSEl->i rate at 120K (1)
72- 74 I3 10-14cm3/s e_E120 The 1σ uncertainty in E120 (2)
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Note (1): Corrected by H2O:H2O selfcollisions.
Note (2): Defined according to Eq.(6) incremented by 3% due to the error
from H2O:H2O selfcollisions.
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Global note:
Note (G1): Table 1: Identification of rotational energy levels of H216O in
the vibrational ground state (Tennyson et al. 2001JPCRD..30..735T 2001JPCRD..30..735T):
------------------------------------------------
ortho-H2O | para-H2O
-----------------------|------------------------
i |Ei |J|tau|Ka|Kc|i |Ei |J|tau|Ka|Kc
|(cm-1) | | | | | |(cm-1) | | | |
------------------------------------------------
1| 23.7944|1| -1| 0| 1| 1| 0.0000|0| 0| 0| 0
2| 42.3717|1| 1| 1| 0| 2| 37.1371|1| 0| 1| 1
3| 79.4964|2| -1| 1| 2| 3| 70.0908|2| -2| 0| 2
4|134.9016|2| 1| 2| 1| 4| 95.1759|2| 0| 1| 1
5|136.7617|3| -3| 0| 3| 5|136.1639|2| 2| 2| 0
6|173.3658|3| -1| 1| 2| 6|142.2785|3| -2| 1| 3
7|212.1564|3| 1| 2| 1| 7|206.3014|3| 0| 2| 2
8|224.8384|4| -3| 1| 4| 8|222.0527|4| -4| 0| 4
9|285.4186|3| 3| 3| 0| 9|275.4970|4| -2| 1| 3
10|300.3623|4| -1| 2| 3|10|285.2193|3| 2| 3| 1
11|325.3479|5| -5| 0| 5|11|315.7795|4| 0| 2| 2
12|382.5169|4| 1| 3| 2|12|326.6255|5| -4| 1| 5
13|399.4575|5| -3| 1| 4|13|383.8425|4| 2| 3| 1
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 11-Feb-2015