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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. https://resolver.caltech.edu/CaltechAUTHORS:20160512-115955441

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Abstract

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
http://dx.doi.org/10.1093/mnras/stw084DOIArticle
https://mnras.oxfordjournals.org/content/457/2/1535PublisherArticle
http://arxiv.org/abs/1601.02386arXivDiscussion Paper
ORCID:
AuthorORCID
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 (https://ciment.ujf-grenoble.fr), which is supported by the Rhône-Alpes region (GRANT CPER07_13 CIRA: http://www.ci-ra.org). 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.
Funders:
Funding AgencyGrant Number
Rhône-Alpes regionCPER07_13 CIRA
NASA/JPL/CaltechUNSPECIFIED
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
DOI:10.1093/mnras/stw084
Record Number:CaltechAUTHORS:20160512-115955441
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20160512-115955441
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
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:12 May 2016 21:12
Last Modified:11 Nov 2021 00:26

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