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Collisional excitation of doubly and triply deuterated ammonia ND_2H and ND_3 by H_2

Daniel, F. and Rist, C. and Faure, A. and Roueff, E. and Gérin, M. and Lis, D. C. and Hily-Blant, P. and Bacmann, A. and Wiesenfeld, L. (2016) Collisional excitation of doubly and triply deuterated ammonia ND_2H and ND_3 by H_2. Monthly Notices of the Royal Astronomical Society, 457 (2). pp. 1535-1549. ISSN 0035-8711. doi:10.1093/mnras/stw084.

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The availability of collisional rate coefficients is a prerequisite for an accurate interpretation of astrophysical observations, since the observed media often harbour densities where molecules are populated under non-local thermodynamic equilibrium conditions. In the current study, we present calculations of rate coefficients suitable to describe the various spin isomers of multiply deuterated ammonia, namely the ND_2H and ND_3 isotopologues. These calculations are based on the most accurate NH_3–H_2 potential energy surface available, which has been modified to describe the geometrical changes induced by the nuclear substitutions. The dynamical calculations are performed within the close-coupling formalism and are carried out in order to provide rate coefficients up to a temperature of T = 50 K. For the various isotopologues/symmetries, we provide rate coefficients for the energy levels below ∼100 cm^(−1). Subsequently, these new rate coefficients are used in astrophysical models aimed at reproducing the NH_2D, ND_2H and ND_3 observations previously reported towards the pre-stellar cores B1b and 16293E. We thus update the estimates of the corresponding column densities and find a reasonable agreement with the previous models. In particular, the ortho-to-para ratios of NH_2D and NHD_2 are found to be consistent with the statistical ratios.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Roueff, E.0000-0002-4949-8562
Lis, D. C.0000-0002-0500-4700
Additional Information:© 2016 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2016 January 8. Received 2016 January 6; in original form 2015 December 14. First published online February 4, 2016. All (or most of) the computations presented in this paper were performed using the CIMENT infrastructure (, which is supported by the Rhône-Alpes region (GRANT CPER07_13 CIRA: DL support for this work was provided by NASA (Herschel OT funding) through an award issued by JPL/Caltech. This work has been supported by the Agence Nationale de la Recherche (ANR-HYDRIDES), contract ANR-12-BS05-0011-01 and by the CNRS national program ‘Physico-Chimie du Milieu Interstellaire’. The authors thanks Q. Ma, P. Dadgigian and A. Van der Avoird for providing some ND_3 cross-sections. We also thank J. Harju for constructive discussions.
Funding AgencyGrant Number
Rhône-Alpes regionCPER07_13 CIRA
Agence Nationale de la Recherche (ANR)ANR-12-BS05-0011-01
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Subject Keywords:molecular data molecular processes scattering
Issue or Number:2
Record Number:CaltechAUTHORS:20160512-115955441
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Official Citation:F. Daniel, C. Rist, A. Faure, E. Roueff, M. Gérin, D. C. Lis, P. Hily-Blant, A. Bacmann, and L. Wiesenfeld Collisional excitation of doubly and triply deuterated ammonia ND2H and ND3 by H2 MNRAS (April 01, 2016) Vol. 457 1535-1549 doi:10.1093/mnras/stw084 First published online February 4, 2016
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:67051
Deposited By: Ruth Sustaita
Deposited On:12 May 2016 21:12
Last Modified:11 Nov 2021 00:26

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