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  • 1
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    Full-dimensional quantum dynamics of CO in collision with H2 (2016)
    American Institute of Physics (AIP)
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    Publication Date: 2016-07-22
    Description: Inelastic scattering computations are presented for collisions of vibrationally and rotationally excited CO with H 2 in full dimension. The computations utilize a newly developed six-dimensional potential energy surface (PES) and the previously reported four-dimensional V12 PES [P. Jankowski et al. , J. Chem. Phys. 138 , 084307 (2013)] and incorporate full angular-momentum coupling. At low collision energies, pure rotational excitation cross sections of CO by para -, ortho -, and normal -H 2 are calculated and convolved to compare with recent measurements. Good agreement with the measured data is shown except for j 1 = 0 → 1 excitation of CO for very low-energy para -H 2 collisions. Rovibrational quenching results are presented for initially excited CO( v 1 j 1 ) levels with v 1 = 1, j 1 = 1–5 and v 1 = 2, j 1 = 0 for collisions with para -H 2 ( v 2 = 0, j 2 = 0) and ortho -H 2 ( v 2 = 0, j 2 = 1) over the kinetic energy range 0.1–1000 cm −1 . The total quenching cross sections are found to have similar magnitudes, but increase (decrease) with j 1 for collision energies above ∼300 cm −1 (below ∼10 cm −1 ). Only minor differences are found between para - and ortho -H 2 colliders for rovibrational and pure rotational transitions, except at very low collision energies. Likewise, pure rotational deexcitation of CO yields similar cross sections for the v 1 = 0 and v 1 = 1 vibrational levels, while rovibrational quenching from v 1 = 2, j 1 = 0 is a factor of ∼5 larger than that from v 1 = 1, j 1 = 0. Details on the PES, computed at the CCSD(T)/aug-cc-pV5Z level, and fitted with an invariant polynomial method, are also presented.
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
    Published by American Institute of Physics (AIP)
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  • 2
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    Chemistry. Beyond platonic molecules (2001)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2001-02-24
    Description: Molecular motion is influenced by quantum mechanics, which thus affect molecular properties such as their reactivity and the ease with which they isomerize. In his Perspective, Bowman describes recent theoretical advances that allow accurate quantum mechanical calculation of molecular motions for ever larger systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bowman, J M -- New York, N.Y. -- Science. 2000 Oct 27;290(5492):724-5.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30309, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/11184203" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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  • 3
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    Reaction pathways (1991)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1991-04-26
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bowman, J M -- New York, N.Y. -- Science. 1991 Apr 26;252(5005):589.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17838492" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 4
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    Theoretical and experimental rate constants for two isotopic modifications of the reaction h + h2 (1990)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1990-07-20
    Description: Theoretical rate constants for two isotopic modifications of the simplest possible chemical reaction, namely, H + D(2) --〉 HD + D and D + H(2) --〉 HD + H, are presented. Experimental results, which have previously been obtained in the higher temperature regime by a shock tube technique, are combined with lower temperature results to give an experimental determination of the rate behavior over the large temperature range approximately 200 to 2000 K. It is now possible to assess the accuracy of ab initio potential energy surface calculations and to judge theoretical chemical kinetic methods.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Michael, J V -- Fisher, J R -- Bowman, J M -- Sun, Q -- New York, N.Y. -- Science. 1990 Jul 20;249(4966):269-71.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17750111" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 5
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    The roaming atom: straying from the reaction path in formaldehyde decomposition (2004)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2004-10-23
    Description: We present a combined experimental and theoretical investigation of formaldehyde (H2CO) dissociation to H2 and CO at energies just above the threshold for competing H elimination. High-resolution state-resolved imaging measurements of the CO velocity distributions reveal two dissociation pathways. The first proceeds through a well-established transition state to produce rotationally excited CO and vibrationally cold H2. The second dissociation pathway yields rotationally cold CO in conjunction with highly vibrationally excited H2. Quasi-classical trajectory calculations performed on a global potential energy surface for H2CO suggest that this second channel represents an intramolecular hydrogen abstraction mechanism: One hydrogen atom explores large regions of the potential energy surface before bonding with the second H atom, bypassing the saddle point entirely.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Townsend, D -- Lahankar, S A -- Lee, S K -- Chambreau, S D -- Suits, A G -- Zhang, X -- Rheinecker, J -- Harding, L B -- Bowman, J M -- New York, N.Y. -- Science. 2004 Nov 12;306(5699):1158-61. Epub 2004 Oct 21.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Stony Brook University, Stony Brook, NY 11794, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/15498970" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 6
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    Signatures of H2CO photodissociation from two electronic states (2006)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2006-03-11
    Description: Even in small molecules, the influence of electronic state on rotational and vibrational product energies is not well understood. Here, we use experiments and theory to address this issue in photodissociation of formaldehyde, H2CO, to the radical products H + HCO. These products result from dissociation from the singlet ground electronic state or the first excited triplet state (T1) of H2CO. Fluorescence spectra reveal a sudden decrease in the HCO rotational energy with increasing photolysis energy accompanied by substantial HCO vibrational excitation. Calculations of the rotational distribution using an ab initio potential energy surface for the T1 state are in very good agreement with experiment and strongly support dominance of the T1 state in the dynamics at the higher photolysis energies.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yin, H M -- Kable, S H -- Zhang, X -- Bowman, J M -- New York, N.Y. -- Science. 2006 Mar 10;311(5766):1443-6.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉School of Chemistry, University of Sydney, Sydney, NSW 2006, Australia.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16527976" target="_blank"〉PubMed〈/a〉
    Keywords: Electrochemistry ; Formaldehyde/*chemistry ; Models, Chemical ; Photochemistry
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 7
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    Quantum deconstruction of the infrared spectrum of CH5+ (2006)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2006-01-10
    Description: We present two quantum calculations of the infrared spectrum of protonated methane (CH5+) using full-dimensional, ab initio-based potential energy and dipole moment surfaces. The calculated spectra compare well with a low-resolution experimental spectrum except below 1000 cm(-1), where the experimental spectrum shows no absorption. The present calculations find substantial absorption features below 1000 cm(-1), in qualitative agreement with earlier classical calculations of the spectrum. The major spectral bands are analyzed in terms of the molecular motions. Of particular interest is an intense feature at 200 cm(-1), which is due to an isomerization mode that connects two equivalent minima. Very recent high-resolution jet-cooled spectra in the CH stretch region (2825 to 3050 cm(-1)) are also reported, and assignments of the band origins are made, based on the present quantum calculations.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Huang, Xinchuan -- McCoy, Anne B -- Bowman, Joel M -- Johnson, Lindsay M -- Savage, Chandra -- Dong, Feng -- Nesbitt, David J -- New York, N.Y. -- Science. 2006 Jan 6;311(5757):60-3.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry and Cherry L. Emerson Center for Scientific Computing, Emory University, Atlanta, GA 30322, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/16400143" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 8
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    Chemistry. Beyond Born-Oppenheimer (2008)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2008-01-05
    Description: 〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bowman, Joel M -- New York, N.Y. -- Science. 2008 Jan 4;319(5859):40-1. doi: 10.1126/science.1152504.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Department of Chemistry, Emory University, Atlanta, GA 30322, USA. jmbowma@emory.edu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/18174423" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 9
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    Dynamics of the reaction of methane with chlorine atom on an accurate potential energy surface (2011)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 2011-10-25
    Description: The reaction of the chlorine atom with methane has been the focus of numerous studies that aim to test, extend, and/or modify our understanding of mode-selective reactivity in polyatomic systems. To this point, theory has largely been unable to provide accurate results in comparison with experiments. Here, we report an accurate global potential energy surface for this reaction. Quasi-classical trajectory calculations using this surface achieve excellent agreement with experiment on the rotational distributions of the hydrogen chloride (HCl) product. For the Cl + CHD(3) --〉 HCl + CD(3) reaction at low collision energies, we confirm the unexpected experimental finding that CH-stretch excitation is no more effective in activating this late-barrier reaction than is the translational energy, which is in contradiction to expectations based on results for many atom-diatom reactions.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Czako, Gabor -- Bowman, Joel M -- New York, N.Y. -- Science. 2011 Oct 21;334(6054):343-6. doi: 10.1126/science.1208514.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Cherry L. Emerson Center for Scientific Computation and Department of Chemistry, Emory University, Atlanta, GA 30322, USA. czako@chem.elte.hu〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/22021853" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
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    Theoretical studies of the energetics and dynamics of chemical reactions (1988)
    American Association for the Advancement of Science (AAAS)
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    Publication Date: 1988-04-22
    Description: Computational studies of basic chemical processes not only provide numbers for comparison with experiment or for use in modeling complex chemical phenomena such as combustion, but also provide insight into the fundamental factors that govern molecular structure and change which cannot be obtained from experiment alone. We summarize the results of three case studies, on HCO, OH + H(2), and O + C(2)H(2), which illustrate the range of problems that can be addressed by using modern theoretical techniques. In all cases, the potential energy surfaces were characterized by using ab initio electronic structure methods. Collisions between molecules leading to reaction or energy transer were described with quantum dynamical methods (HCO), classical trajectory techniques (HCO and OH + H(2)), and statistical methods (HCO, OH + H(2), and O + C(2)H(2)). We can anticipate dramatic increases in the scope of this work as new generations of computers are introduced and as new chemistry software is developed to exploit these computers.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Dunning, T H Jr -- Harding, L B -- Wagner, A F -- Schatz, G C -- Bowman, J M -- New York, N.Y. -- Science. 1988 Apr 22;240(4851):453-9.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/17784067" target="_blank"〉PubMed〈/a〉
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
    Published by American Association for the Advancement of Science (AAAS)
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