| Temperature-Dependent, Effective Structures of the 14NH3 and 14ND3 Molecules. | |
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MedLine Citation:
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PMID: 22471770 Owner: NLM Status: Publisher |
Abstract/OtherAbstract:
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Measurements result in effective, usually temperature-dependent structural parameters of molecules, and never directly in equilibrium structures, which are theoretical constructs. A recent high-accuracy semiglobal potential energy surface (PES) of the electronic ground state of the ammonia molecule, called NH3-Y2010 (J. Mol. Spectrosc. 2011, 268, 123), which exhibits mass-independent equilibrium NH bond length and HNH bond angle of 1.0109 A and 106.75 deg, respectively, is employed together with the variational nuclear motion code GENIUSH (J. Chem. Phys. 2009, 130, 134112, ibid. 2011, 134, 074105) to determine directly measurable, effective structural parameters of the14NH3 and 14ND3 molecules. The effective rg- and ra-type NH(ND) distances determined at 300 K are 1.0307(1.0254) and 1.0256(1.0217) A, respectively, with an estimated accuracy of 2x10-4 A. The effective thetag HNH and DND bond angles at 300 K are 106.91 deg and 106.85 deg, respectively. The root-mean-square amplitudes of vibration, lg, for the NH(ND) distances at 300 K are 0.073(0.062) A. These structural parameters confirm the less accurate results of a room-temperature gas-electron-diffraction study (J. Chem. Phys. 1968, 49, 2488, all data in A): $r_{\rm g}$(NH) = 1.030(2), $l_{\rm g}$(NH) = 0.073(2), $r_{\rm g}$(ND) = 1.027(3), and $l_{\rm g}$(ND) = 0.061(2). The computed difference in the $r_{\mr{g},T}$(NH) bond lengths of the two spin isomers (ortho and para forms) of $^{14}$NH$_3$ is $3 \times 10^{-5}$ \AA\ at 0~K, the difference diminishes at temperatures of about 30--50 K. |
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Authors:
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Istvan Szabo; Csaba Fabri; Gabor Czako; Edit Matyus; Attila G Császár |
Publication Detail:
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Type: JOURNAL ARTICLE Date: 2012-4-3 |
Journal Detail:
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Title: The journal of physical chemistry. A Volume: - ISSN: 1520-5215 ISO Abbreviation: - Publication Date: 2012 Apr |
Date Detail:
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Created Date: 2012-4-4 Completed Date: - Revised Date: - |
Medline Journal Info:
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Nlm Unique ID: 9890903 Medline TA: J Phys Chem A Country: - |
Other Details:
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Languages: ENG Pagination: - Citation Subset: - |
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From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine
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