Influence of a new potential energy surface on the 
rotational (de)excitation of H$_{\mathsf 2}$O by H$_{\mathsf 2}$ at low temperature

Dubernet, Marie‐Lise; Daniel, F.; Grosjean, Alain; Fauré, Alexandre; Valiron, P.; Wernli, Michael; Wiesenfeld, Laurent; Rist, Claire; Noga, Jozef; Tennyson, Jonathan

doi:10.1051/0004-6361:20065804

Cited by 81 publications

(110 citation statements)

References 27 publications

(82 reference statements)

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“…To characterize the two gas components at R2 in terms of excitation conditions, we ran the radex non-LTE molecular LVG radiative transfer code (van der Tak et al 2007) in plane-parallel geometry, with collisional rate coefficients from Dubernet et al (2006Dubernet et al ( , 2009 and Daniel et al (2010Daniel et al ( , 2011 and molecular data from the Leiden Atomic and Molecular Database (LAMDA 4 , Schöier et al 2005). A grid of models with density ranging between 10 4 cm −3 and 10 8 cm −3 and temperatures ranging between 100 K and 1600 K was built.…”

Section: Two Gas Components In Shocked H 2 O Emissionmentioning

confidence: 99%

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Santangelo

Nisini

Codella

et al. 2014

A&A

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Context. Water is a key molecule in protostellar environments because its line emission is very sensitive to both the chemistry and the physical conditions of the gas. Observations of H 2 O line emission from low-mass protostars and their associated outflows performed with HIFI onboard the Herschel Space Observatory have highlighted the complexity of H 2 O line profiles, in which different kinematic components can be distinguished. Aims. The goal is to study the spatial distribution of H 2 O, in particular of the different kinematic components detected in H 2 O emission, at two bright shocked regions along IRAS 4A, one of the strongest H 2 O emitters among the Class 0 outflows. Methods. We obtained Herschel-PACS maps of the IRAS 4A outflow and HIFI observations of two shocked positions. The largest HIFI beam of 38 at 557 GHz was mapped in several key water lines with different upper energy levels, to reveal possible spatial variations of the line profiles. A large velocity gradient (LVG) analysis was performed to determine the excitation conditions of the gas. Results. We detect four H 2 O lines and CO (16−15) at the two selected shocked positions. In addition, transitions from related outflow and envelope tracers are detected. Different gas components associated with the shock are identified in the H 2 O emission. In particular, at the head of the red lobe of the outflow, two distinct gas components with different excitation conditions are distinguished in the HIFI emission maps: a compact component, detected in the ground-state water lines, and a more extended one. Assuming that these two components correspond to two different temperature components observed in previous H 2 O and CO studies, the LVG analysis of the H 2 O emission suggests that the compact (about 3 , corresponding to about 700 AU) component is associated with a hot (T ∼ 1000 K) gas with densities n H 2 ∼ (1−4) × 10 5 cm −3 , whereas the extended (10 −17 , corresponding to 2400−4000 AU) one traces a warm (T ∼ 300−500 K) and dense gas (n H 2 ∼ (3−5) × 10 7 cm −3 ). Finally, using the CO (16−15) emission observed at R2 and assuming a typical CO/H 2 abundance of 10 −4 , we estimate the H 2 O/H 2 abundance of the warm and hot components to be (7−10) × 10 −7 and (3−7) × 10 −5 . Conclusions. Our data allowed us, for the first time, to resolve spatially the two temperature components previously observed with HIFI and PACS. We propose that the compact hot component may be associated with the jet that impacts the surrounding material, whereas the warm, dense, and extended component originates from the compression of the ambient gas by the propagating flow.

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Section: Two Gas Components In Shocked H 2 O Emissionmentioning

confidence: 99%

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Santangelo

Nisini

Codella

et al. 2014

A&A

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“…Using this newly determined 5D PES for H 2 -H 2 O, Dubernet et al (2006b) provided an extended and revised set of rate coefficients for de-excitation of the lowest 10 rotational levels of o/p-H 2 O by collisions with p-H 2 ( j 2 = 0) and o-H 2 ( j 2 = 1), for kinetic temperatures from 5 K to 20 K.…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

“…The influence of the new PES on collisions with both p-H 2 ( j 2 = 0) and o-H 2 ( j 2 = 1) is expected to become less pronounced at higher temperatures. Faure et al (2007) provided rate coefficients for rotational de-excitation among the lowest 45 rotational levels of o/p-H 2 O colliding with o/p-H 2 in the temperature range 20-2000 K. This set is a combination of various data: 1) data obtained with quasi classical trajectory (QCT) calculations with the H 2 molecule assumed to be rotationally thermalized at kinetic temperature and calculated between 100 K and 2000 K; 2) the values at 20 K are CC calculations from Dubernet et al (2006b) for the first 5 levels and are equal to values at 100 K for all other levels; 3) scaled H 2 O-He results from Green et al (1993) for the weakest rate coefficients. A preliminary comparison (Faure et al 2007) with current CC calculations concerning low lying levels of water at high temperature showed that QCT thermalized rate coefficients were accurate to within a factor of 1-3 for the dominant transitions, i.e.…”

Section: Article Published By Edp Sciencesmentioning

confidence: 99%

“…In the current calculations we use the same expansion of the Faure et al (2005a) 5D PES as in Dubernet et al (2006b), where details can be found. For this PES, inaccuracies in inelastic cross sections might come from different sources: propagation parameters, description of the rotational Hamiltonians of the 2 molecules, sizes of H 2 O and H 2 rotational basis sets, (Hutson & Green 1994;McBane 2004).…”

Section: Description Of the Calculationsmentioning

confidence: 99%

“…For this PES, inaccuracies in inelastic cross sections might come from different sources: propagation parameters, description of the rotational Hamiltonians of the 2 molecules, sizes of H 2 O and H 2 rotational basis sets, (Hutson & Green 1994;McBane 2004). Parameters of the propagation are optimized as was done in Dubernet & Grosjean (2002); Grosjean et al (2003); Dubernet et al (2006b). Identically to Dubernet et al (2006b), the H 2 energy levels are the experimental energies of Dabrowski (1984) and the H 2 O energy levels and eigenfunctions are obtained by diagonalisation of the effective hamiltonian of Kyrö (1981), compatible with the symmetries of the PES (Dubernet & Grosjean 2002;Grosjean et al 2003;Dubernet et al 2006b).…”

Section: Description Of the Calculationsmentioning

confidence: 99%

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Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

Dubernet

Daniel

Grosjean

et al. 2009

A&A

Self Cite

102

163

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Aims. Our objective is to obtain the best possible set of rotational (de)-excitation state-to-state and effective rate coefficients for temperatures up to 1500 K. We present state-to-state rate coefficients among the 45 lowest levels of o-H 2 O with H 2 ( j 2 = 0) and Δ j 2 = 0, +2, as well as with H 2 ( j 2 = 2) and Δ j 2 = 0, −2. In addition and only for the 10 lowest energy levels of o-H 2 O, we provide state-to-state rate coefficients involving j 2 = 4 with Δ j 2 = 0, −2 and j 2 = 2 with Δ j 2 = +2. We give estimates of effective rate coefficients for j 2 = 6, 8. Methods. Calculations are performed with the close coupling (CC) method over the whole energy range, using the same 5D potential energy surface (PES) as the one employed in our latest publication on water. We perform comparisons with coupled states (CS) calculations, with thermalized quasi-classical trajectory (QCT) calculations using the same PES and with previous quantum calculations obtained between T = 20 K and T = 140 K with a different PES. Results. We find that the CS approximation fares extremely badly even at high energy for j 2 different from zero. Comparisons with thermalized QCT calculations show large factors at intermediate temperatures and factors from 1 to 3 at high temperature for the strongest rate coefficients. Finally we stress that scaled collisional rate coefficients obtained with He cannot be used in place of collisional rate coefficients with H 2 .

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A Monte Carlo error estimator for the expansion of rigid-rotor potential energy surfaces

Rist

Fauré

2011

J Math Chem

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Influence of a new potential energy surface on the rotational (de)excitation of H$_{\mathsf 2}$O by H$_{\mathsf 2}$ at low temperature

Cited by 81 publications

References 27 publications

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature

A Monte Carlo error estimator for the expansion of rigid-rotor potential energy surfaces

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Influence of a new potential energy surface on the rotational (de)excitation of H$_{\mathsf 2}$O by H$_{\mathsf 2}$ at low temperature

Cited by 81 publications

References 27 publications

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Water distribution in shocked regions of the NGC 1333-IRAS 4A protostellar outflow

Rotational excitation of ortho-H2O by para-H2 (j2 = 0, 2, 4, 6, 8) at high temperature

A Monte Carlo error estimator for the expansion of rigid-rotor potential energy surfaces

Contact Info

Product

Resources

About

Rotational excitation of ortho-H₂O by para-H₂ (j₂ = 0, 2, 4, 6, 8) at high temperature